Hookworm infection Anchylostomiasis

Hookworm infection Anchylostomiasis Ancylostomiasis is also known as miner's anaemia, tunnel disease, brickmaker's anaemia and Egyptian chlorosis. Canine hookworms include Ancylostoma caninum, A.

Helminthiasis may also refer to ancylostomiasis, but this term also refers to all other parasitic worm diseases as well Ancylostomiasis is a hookworm disease caused by infection with Ancylostoma hookworms. The name is derived from Greek ancylos αγκύλος "crooked, bent" and stoma στόμα "mouth". braziliense, and Uncinaria stenocephala. Hookworm infection is one of the most common diagnoses in canine practice, and A. caninum is by far the most prevalent species involved. Ancylostoma eggs were identified in 19% of canine fecal samples collected from various locales in the United States [6]. Ancylostoma caninum infections can be acquired by vertical (transmammary) transmission, percutaneous invasion, or ingestion of infective third-stage larvae or paratenic hosts. In mature dogs with some acquired immunity, infective larvae may not develop directly into adults, but rather migrate to somatic tissues such as kidney and skeletal muscle, where they undergo prolonged arrested development [7]. These arrested larvae are most commonly reactivated by the hormones of pregnancy and lactation, and larvae are transmitted to suckling pups in the bitch’s milk. Although hookworm infection is observed in dogs of all ages, pups and juveniles are more likely to exhibit clinical signs of disease, including anemia, weakness, melena, anorexia, and weight loss or poor growth. As with most parasitisms, clinical signs are exacerbated by malnutrition, stress, or concurrent disease. Hookworm disease (ancylostomosis) has been classified as four distinct syndromes which vary with the age, route of infection, or overall health status of the animal. In peracute ancylostomosis, suckling pups around 2–3 weeks of age die of severe anemia with no preceding clinical signs, due to overwhelming hookworm infections acquired through the transmammary route. Acute ancylostomosis involves slightly older or weaned pups that survive long enough to develop melena and signs of severe anemia. Again, transmammary infection is the usual route. The two remaining classifications of ancylostomosis occur in mature dogs that are either repeatedly exposed to L3 stages or are continuously reinfected with larvae activated from their arrested, somatic pools. Uncompensated ancylostomosis occurs when malnutrition or co-morbid disease render an animal incapable of managing hookworm insults through immunologic or general defense mechanisms. In contrast, no clinical signs are seen in dogs with compensated ancylostomosis, which is a term used to describe recurrent infections that are partially controlled, but not eliminated, by host mechanisms. Compensated ancylostomosis is typically recognized when fecal examinations after repeated treatments document the incessant reappearance of hookworm eggs. Products labeled for treatment or removal of Ancylostoma caninum are the appropriate therapeutic choice for apparently healthy dogs or those with moderate signs of ancylostomosis (ie, compensated and uncompensated cases). Suckling pups with acute ancylostomosis require immediate and vigorous medical attention. Pyrantel pamoate/embonate is the preferred anthelmintic for this syndrome, due to its speed of activity and broad safety in debilitated animals. Ancillary medical management (eg, iron supplementation) is critical, but pups with acute ancylostomosis often make very dramatic recoveries once the immediate source of blood loss has been eliminated. By definition, anthelmintic treatment would arrive too late to salvage pups with peracute ancylostomosis, but surviving littermates should be treated promptly as for the acute syndrome. Specific regimens of pyrantel pamoate have been designed to reduce the clinical impact of hookworm infections in suckling pups. These are described in greater detail in the section on Toxocara canis. Current standards of care support the maintenance of all canine patients on some form of heartworm prevention, and all currently marketed Dirofilaria preventives are anthelmintics of the macrocyclic lactone (ML) class. Several heartworm preventive products have been developed in which the ML component is combined with other anthelmintics, including pyrimidines, to provide a broader spectrum of nematode control. Because most MLs also exhibit activity against hookworms, some of these combination products achieve higher efficacy against hookworms than either component used singly. For example, HeartGard Plus (ivermectin plus pyrantel pamoate) was more than 99% effective against adult Uncinaria stenocephala whereas pyrantel pamoate alone exhibited 93.4–96.3% efficacy [8]. Regular, monthly administration of such combination products reduces environmental contamination with hookworm eggs, and thereby reduces the risk of compensated or uncompensated ancylostomosis in mature dogs. Uncinaria stenocephala is a less common hookworm of dogs that is most often acquired through ingestion of third-stage larvae (L3s). Uncinaria is more restricted in its geographic distribution than Ancylostoma caninum, occurring more frequently in Europe, Canada, and the northern tier of the United States. Uncinaria eggs were found in only 1.02% of canine fecal samples collected from around the United States [6]. Uncinaria ingests plasma proteins rather than whole blood, so clinical signs are primarily related to the gradual loss of vital nutrients. Ancylostoma braziliense is another fairly nonpathogenic hookworm of dogs that is limited to tropical and subtropical climates. Routine Uncinaria and A. braziliense infections can be managed with approved anthelmintics containing pyrantel pamoate/embonate. Transmammary transmission does not occur with either species, so special regimens for suckling pups are not required. Some monthly heartworm preventives are also labeled for efficacy against U. stenocephala and A. braziliense (eg, HeartGard Plus). Regular control is advisable in endemic areas because both U. braziliense can cause a zoonotic condition known as cutaneous larva migrans [9].

29/07/2022

Hookworm infections are common in the tropics and subtropics The prevalence of hookworm infection is highest in sub-Saharan Africa, followed by Asia, Latin America, and the Caribbean. Infection is rare in regions with less than 40 inches of rainfall annually.
There are two major species of hookworm that cause human infection: Ancylostoma duodenale (in Mediterranean countries, Iran, India, Pakistan, and the Far East) and Necator americanus (in North and South America, Central Africa, Indonesia, islands of the South Pacific, and parts of India).
In addition, a hookworm of dogs and cats, Ancylostoma ceylanicum, has been recognized as a widely prevalent cause of human zoonotic infections in India, Southeast Asia, tropical Australia, and some Melanesian Pacific Islands
EPIDEMIOLOGY AND LIFE CYCLE
It is estimated that approximately 500 million people are infected with hookworms worldwide. Globally, hookworm infections have their major impact not by causing death but rather by contributing to morbidity especially due to anemia, including about 4 million disability-adjusted life years in 2010 The prevalence of hookworm infection in rural areas of the southeastern United States in the early 20th century was high Extensive control efforts diminished the prevalence within the United States; regions in the southeastern United States that have poor sanitation still are sites of hookworm infection
Three conditions are important for transmission of hookworm infection: human f***l contamination of soil, favorable soil conditions for larval survival (moisture, warmth, shade), and contact of human skin with contaminated soil. Individuals who walk barefoot or with open footwear in f***lly contaminated soil are at risk for infection; risk groups include residents of endemic areas, tourists, and infantry troops

29/07/2022

Hookworm infection is caused by roundworms. The disease affects the small intestine and lungs.

Causes
The infection is caused by infestation with any of the following roundworms:

Necator americanus
Ancylostoma duodenale
Ancylostoma ceylanicum
Ancylostoma braziliense
The first two roundworms affect humans only. The last two types also occur in animals.

Hookworm disease is common in the moist tropics and subtropics. In developing nations, the disease leads to the death of many children by increasing their risk for infections that their bodies would normally fight off.
There is very little risk of getting the disease in the United States because of advances in sanitation and waste control. The important factor in getting the disease is walking barefoot on ground where there are f***s of people who are infected with hookworm.
The larvae (immature form of the worm) enter the skin. The larvae move to the lungs via the bloodstream and enter the airways. The worms are about one-half inch (1 centimeter) long.
After traveling up the windpipe, the larvae are swallowed. After the larvae are swallowed, they infect the small intestine. They develop into adult worms and live there for 1 or more years. The worms attach to the intestinal wall and suck blood, which can result in iron deficiency anemia and protein loss. Adult worms and larvae are released in the f***s.

27/04/2022

High-intensity hookworm infections occur among both school-age children and adults, unlike the soil-transmitted helminths Ascaris and whipworm. High-intensity infections with these worms are less common among adults. The most serious effects of hookworm infection are the development of anemia and protein deficiency caused by blood loss at the site of the intestinal attachment of the adult worms. When children are continuously infected by many worms, the loss of iron and protein can re**rd growth and mental development.

27/04/2022

Known distribution of Ancylostoma ceylanicum infections in Southeast Asia and the Pacific. Human infections from 2013 or earlier are depicted in orange, human infections after 2013 to date are depicted in purple, and all canine infections are highlighted in black. Not depicted here are studies of canine A. ceylanicum infections from Madagascar, Kenya, Tanzania, and South Africa.
Citation: The American Journal of Tropical Medicine and Hygiene 103, 1; 10.4269/ajtmh.20-0060
The inconsistency in diagnostic tools used to estimate infection prevalence may additionally contribute to this underestimation.39 In the context of some studies that used a traditional microscopy-based gold standard diagnosis tool, only hookworm-positive samples were further investigated for species-specific infections using molecular tools.25,30 Not only does this lead to an underestimation of overall hookworm prevalence,40 but it also underestimates the proportion of A. ceylanicum infections even further,25 owing to the relatively lower egg-shedding intensities of A. ceylanicum–infected individuals than those infected with N. americanus.41
Despite the increased availability and application of molecular diagnostic assays,40 there remains a lack of large-scale mapping of A. ceylanicum in areas other than Southeast Asia and the Pacific, with a clear lack of available data in regard to infection prevalence and intensity, particularly in human populations. This lack of knowledge is partly due to the application of microscopy-based diagnostic tools that are not able to differentiate between hookworm species.42 Apart from Southeast Asia and the Pacific, A. ceylanicum has also been reported in 3% of canines in Tanzania.43 To date, the global distribution of cases in humans reflects that of its distribution in dogs. During the previous 6 years after publication of Traub’s 2013 review, the focus of STH research has been on molecular biological areas such as genomics, transcriptomics, and diagnostics.44 At the same time, diagnostic tool application is shifting from invasive endoscopy38 to molecular laboratory–based techniques such as semi-nested polymerase chain reaction (PCR)-RFLP, quantitative PCR (qPCR), and multiplexed-tandem qPCR.28,45 Moving toward these advanced molecular biology–based diagnostic tools using PCR systems can prove beneficial in increasing general knowledge of hookworm infection prevalence, the species-specific burden they cause and examining effects of coinfections within hosts.46 Currently, however, novel diagnostic techniques are limited to research settings and still need to be completely transferable to the endemic field in regard to resources, expertise, and simple feasibility in remote settings.47
As evidently shown within the literature, A. ceylanicum continues to present itself as an increasingly emergent zoonosis, with a potentially wider than previously assumed geographical distribution. For the majority of countries, there is a paucity of epidemiological information available, which would serve as the basis for monitoring and diagnosing infections with this zoonosis for both clinical and population settings. Of the 13 epidemiological studies on Ancylostoma ceylanicum retrieved from Google Scholar (since 2013) (70 total hits), nearly all used molecular-based screening to further identify hookworms to a species level. Traub hypothesized the emergence of A. ceylanicum owing to multiple factors, including wide-scale mass deworming programs, resulting in the disproportional increase in infective larvae in the environment compared with that of N. americanus larvae, exacerbated by the lack of an “allergy-based” elimination of any new incoming larvae of “unnatural” hookworms. If this is due to differential benzimidazole drug efficacy for different hookworm species remains unclear.
There is a clear need for further in-depth investigation of A. ceylanicum infection prevalence, intensity, and morbidity data in human hosts worldwide. These data will aid in mapping a more detailed picture of STH infections, inform governmental agencies about targeted treatment programs (including One Health approaches), and ultimately contribute to an eradication of not only hookworm infections but also helminth infections more broadly.

29/11/2021

ookworm infection is an infection of the intestines that can cause an itchy rash, respiratory and gastrointestinal problems, and eventually iron deficiency anemia due to ongoing loss of blood.
People can become infected when walking barefoot because hookworm larvae live in the soil and can pe*****te the skin.
At first, people may have an itchy rash where the larvae pe*****te the skin, then fever, coughing, and wheezing or abdominal pain, loss of appetite, and diarrhea.
Severe, chronic infections can cause loss of blood and anemia that is sometimes severe enough to cause fatigue and occasionally heart failure and widespread swelling.
Doctors diagnose the infection by identifying hookworm eggs in a stool sample.
The infection is treated with antiparasitic drugs such as albendazole.
(See also Overview of Parasitic Infections.)

Worldwide, between 576 and 740 million people are infected with hookworms, which are intestinal roundworms. The infection is most common in tropical areas where sanitation is poor. Hookworms thrive in warm, moist places.

Two species of hookworm cause infection in people:

Ancylostoma duodenale
Necator americanus
Both species are present in moist, hot areas of Africa, Asia, and the Americas. Ancylostoma duodenale is present in the Middle East, North Africa, and southern Europe. Necator americanus is present mainly in the Americas and Australia. It once was common in the southern part of the United States but is now rare there. Finally, Ancylostoma ceylanicum, a hookworm of dogs, cats, and hamsters present in parts of Asia and some South Pacific islands, can complete its life cycle in humans and on occasion causes hookworm disease.

Hookworm infection is an infection of the intestines that can cause an itchy rash, respiratory and gastrointestinal prob...
29/11/2021

Hookworm infection is an infection of the intestines that can cause an itchy rash, respiratory and gastrointestinal problems, and eventually iron deficiency anemia due to ongoing loss of blood. People can become infected when walking barefoot because hookworm larvae live in the soil and can pe*****te the skin.

HookwormsCanine hookworms include Ancylostoma caninum, A. braziliense, and Uncinaria stenocephala. Hookworm infection is...
28/11/2021

Hookworms
Canine hookworms include Ancylostoma caninum, A. braziliense, and Uncinaria stenocephala. Hookworm infection is one of the most common diagnoses in canine practice, and A. caninum is by far the most prevalent species involved. Ancylostoma eggs were identified in 19% of canine f***l samples collected from various locales in the United States
Ancylostoma caninum infections can be acquired by vertical (transmammary) transmission, percutaneous invasion, or ingestion of infective third-stage larvae or paratenic hosts. In mature dogs with some acquired immunity, infective larvae may not develop directly into adults, but rather migrate to somatic tissues such as kidney and skeletal muscle, where they undergo prolonged arrested development [7]. These arrested larvae are most commonly reactivated by the hormones of pregnancy and lactation, and larvae are transmitted to suckling pups in the bitch’s milk. Although hookworm infection is observed in dogs of all ages, pups and juveniles are more likely to exhibit clinical signs of disease, including anemia, weakness, melena, anorexia, and weight loss or poor growth. As with most parasitisms, clinical signs are exacerbated by malnutrition, stress, or concurrent disease.
Hookworm disease (ancylostomosis) has been classified as four distinct syndromes which vary with the age, route of infection, or overall health status of the animal. In peracute ancylostomosis, suckling pups around 2–3 weeks of age die of severe anemia with no preceding clinical signs, due to overwhelming hookworm infections acquired through the transmammary route. Acute ancylostomosis involves slightly older or weaned pups that survive long enough to develop melena and signs of severe anemia. Again, transmammary infection is the usual route. The two remaining classifications of ancylostomosis occur in mature dogs that are either repeatedly exposed to L3 stages or are continuously reinfected with larvae activated from their arrested, somatic pools. Uncompensated ancylostomosis occurs when malnutrition or co-morbid disease render an animal incapable of managing hookworm insults through immunologic or general defense mechanisms. In contrast, no clinical signs are seen in dogs with compensated ancylostomosis, which is a term used to describe recurrent infections that are partially controlled, but not eliminated, by host mechanisms. Compensated ancylostomosis is typically recognized when f***l examinations after repeated treatments document the incessant reappearance of hookworm eggs.
Products labeled for treatment or removal of Ancylostoma caninum are the appropriate therapeutic choice for apparently healthy dogs or those with moderate signs of ancylostomosis (ie, compensated and uncompensated cases). Suckling pups with acute ancylostomosis require immediate and vigorous medical attention. Pyrantel pamoate/embonate is the preferred anthelmintic for this syndrome, due to its speed of activity and broad safety in debilitated animals. Ancillary medical management (eg, iron supplementation) is critical, but pups with acute ancylostomosis often make very dramatic recoveries once the immediate source of blood loss has been eliminated. By definition, anthelmintic treatment would arrive too late to salvage pups with peracute ancylostomosis, but surviving littermates should be treated promptly as for the acute syndrome.
Specific regimens of pyrantel pamoate have been designed to reduce the clinical impact of hookworm infections in suckling pups. These are described in greater detail in the section on Toxocara canis.
Current standards of care support the maintenance of all canine patients on some form of heartworm prevention, and all currently marketed Dirofilaria preventives are anthelmintics of the macrocyclic lactone (ML) class. Several heartworm preventive products have been developed in which the ML component is combined with other anthelmintics, including pyrimidines, to provide a broader spectrum of nematode control. Because most MLs also exhibit activity against hookworms, some of these combination products achieve higher efficacy against hookworms than either component used singly. For example, HeartGard Plus (ivermectin plus pyrantel pamoate) was more than 99% effective against adult Uncinaria stenocephala whereas pyrantel pamoate alone exhibited 93.4–96.3% efficacy [8]. Regular, monthly administration of such combination products reduces environmental contamination with hookworm eggs, and thereby reduces the risk of compensated or uncompensated ancylostomosis in mature dogs.
Uncinaria stenocephala is a less common hookworm of dogs that is most often acquired through ingestion of third-stage larvae (L3s). Uncinaria is more restricted in its geographic distribution than Ancylostoma caninum, occurring more frequently in Europe, Canada, and the northern tier of the United States. Uncinaria eggs were found in only 1.02% of canine f***l samples collected from around the United States [6]. Uncinaria ingests plasma proteins rather than whole blood, so clinical signs are primarily related to the gradual loss of vital nutrients. Ancylostoma braziliense is another fairly nonpathogenic hookworm of dogs that is limited to tropical and subtropical climates.
Routine Uncinaria and A. braziliense infections can be managed with approved anthelmintics containing pyrantel pamoate/embonate. Transmammary transmission does not occur with either species, so special regimens for suckling pups are not required. Some monthly heartworm preventives are also labeled for efficacy against U. stenocephala and A. braziliense (eg, HeartGard Plus). Regular control is advisable in endemic areas because both U. stenocephala and A. braziliense can cause a zoonotic condition known as cutaneous larva migrans

28/11/2021

Early findings of adult Oesophagostomum worms
Apart from the description of clinical cases with tissue-dwelling juvenile worms, lumen-dwelling adult worms have been found in three instances, all in the early 1900s, and all in patients treated with ancient drugs for ancylostomiasis. Leiper's description, referred to in the introduction to this paper, was based on the accidental finding of adult specimens of O. apiostomum while searching for hookworms in a stool sample from a Nigerian patient (Leiper, 1911). Shortly after, in a report on helminth infections among prisoners in the same area of Northern Nigeria, Johnson (1913) examined stool samples from all 200 prisoners in Zungeru prison. Among them 42% appeared to excrete hookworm eggs. Upon treatment of all prisoners with thymol or eucalyptus, Oesophagostomum worms were found in eight but the numbers of worms were small. In seven of the eight cases, hookworms were expelled as well. No symptoms could be attributed to the Oesophagostomum infections. Finally, in a helminthological survey in man and a variety of animals in Guinea, Henry and Joyeux (1920) made mention of a similar finding of some Oesophagostomum worms after treatment of two hookworm patients (Brumpt, 1936).

Parasitic infestationsMetazoan infestations: ancylostomiasis (hookworm infestation), angiostrongyliasis, ascariasis, clo...
28/11/2021

Parasitic infestations
Metazoan infestations: ancylostomiasis (hookworm infestation), angiostrongyliasis, ascariasis, clonorchiasis, cysticercosis, echinococcosis (hydatid cyst), fascioliasis, fasciolopsiasis, filariasis, gnathostomiasis, loiasis, onchocerciasis, paragonimiasis, schistosomiasis, strongyloidiasis, toxocariasis, trichinellosis, visceral larva migrans (toxocariasis)
Arthropod infestations: scabies
Certain fungal and bacterial infections: allergic pulmonary aspergillosis, chronic tuberculosis (occasionally), coccidioidomycosis, disseminated histoplasmosis, Pneumocystis pneumoniae infection, scarlet fever
Allergic disorders: bronchial asthma, atopic eczema, hay fever, allergic vasculitis, Stevens–Johnson syndrome, drug sensitivity (gold, sulphonamides, penicillin)
Graft-versus-host reaction
Skin diseases: pemphigus, bullous pemphigoid, eczema, psoriasis, herpes gestationis, subcutaneous eosinophilic angiolymphoid hyperplasia with eosinophilia, eosinophilic lymphofolliculosis (Kimura's disease), granulomatous dermatitis with eosinophilia (Well's disease), diffuse fasciitis with eosinophilia (Schulman's syndrome)
Postinfection rebound eosinophilia
Reactive ‘pulmonary’ eosinophilia
Löffler's syndrome (pulmonary infiltration with eosinophilia), tropical pulmonary eosinophilia
Idiopathic hypereosinophilic syndrome
Leukemias, myeloproliferative neoplasms, myeloid and lymphoid neoplasms with abnormalities of PDGFRA, PDGFB or FGFR1
Other malignant diseases: Mycosis fungoides, Sézary syndrome, Hodgkin's disease, other lymphomas (T-cell), angioimmunoblastic lymphadenopathy, carcinoma (usually with metastasis), multiple myeloma, heavy chain disease
Connective tissue disorders
Churg–Strauss syndrome and systemic necrotizing vasculitis (variants of polyarteritis nodosa), systemic sclerosis, rheumatoid arthritis
Thrombocytopenia with absent radii
Certain disorders of neutrophils: Job's syndrome, severe congenital neutropenia, familial benign chronic neutropenia, cyclical neutropenia
Wiskott–Aldrich syndrome
Cyclical eosinophilia with angioedema
Hereditary eosinophilia
Miscellaneous: ulcerative colitis, Crohn's disease, eosinophilic gastroenteritis, Goodpasture's syndrome, pancreatitis, chronic active hepatitis, after splenectomy, after irradiation of intra-abdominal tumors

28/11/2021

Ancylostomiasis

•
Angiostrongyliasis

•
Anisakiasis

•
Baylisascariasis

•
Dirofilariasis

•
Gnathostomiasis
○
Larva migrans profundus, nodular migratory eosinophilic panniculitis, spiruroid larva migrans, wandering swelling, Yangtze edema

•
Toxocariasis

•
Trichinellosis

Etiology/Pathogenesis
Environmental Exposure
•
Animal exposures: Cutaneous larva migrans, toxocariasis, gnathostomiasis, baylisascariasis

•
Mosquito/animal exposure: Dirofilariasis, North American Brugia

•
Undercooked meat/fish or raw vegetables: Trichinellosis, anisakiasis, angiostrongyliasis

Infectious Agents
•
Nematodes in which life cycle is normally completed outside of humans
○
Incidentally infect humans

○
Lead to tissue pathology (masses, lesions)

•
Ancylostoma caninum, Ancylostoma braziliense, and other species (mammal hookworms causing cutaneous larva migrans)

•
Angiostrongylus cantonensis (rat lung worm) and An giostrongylus (Parastrongylus) costaricensis

•
Anisakis simplex and Pseudoterranova decipiens (cod worm)

•
Baylisascaris procyonis (raccoon lung worm)

•
Dirofilaria immitis, Dirofilaria repens, Dirofilaria ursi, Dirofilaria tenuis (dog, dog, bear, and raccoon heartworm)

•
Gnathostoma spinigerum and Gnathostoma hispidum (larva migrans profundus)

•
North American Brugia (species unclassified)

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Toxocara canis and Toxocara cati (larva migrans)

•
Trichinella spiralis, Trichinella pseudospiralis, Trichinella nativa, Trichinella nelsoni, Trichinella britovi, and Trichinella papuae (trichinellosis)

Clinical Issues
Presentation
•
Burrowing skin eruptions
○
Cutaneous larva migrans (CLM) (2 cm/day) from Ancylostoma
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Red, indurated, haphazard burrows

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Usually on lower extremities or any surface in contact with ground

○
Larva migrans profundus (LMP) (1 cm/hour) from Gnathostoma
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Begins with abdominal pain, fever, anorexia, vomiting

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Proceeds with migration to intermittent, painful, itchy skin lesions, which turns to edema when migration subsides

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May migrate to any part of body and cause symptoms due to specific organ involvement

•
Eosinophilic meningitis (Angiostrongylus is most common cause)

•
Toxocariasis and baylisascariasis
○
Visceral larva migrans (VLM)
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Severe reaction to migrating larvae with organ-specific manifestations

○
Covert toxocariasis (CT)
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Chronic exposure with fever, abdominal pain, headache, cough (wheezing), sleep disturbances, hepatomegaly, lymphadenitis

○
Ocular larva migrans (OLM)
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Single worm, single eye involved with erythema, white/fixed pupil, retinal damage, orbital inflammation, and strabismus

–
Granulomatous nodules of eye may also be D. tenuis

○
Other organ involvement with Baylisascaris can occur due to wandering nature and continued growth of worm, including neurological involvement

•
Solitary mass in lung (D. immitis)
○
Rarely, Ascaris lumbricoides, human hookworm, and S. stercoralis may arrest in pulmonary stage and cause pneumonitis (eosinophilic) or granulomatous lesions

•
Solitary mass in skin/subcutaneous tissues (D. repens, D. ursi, D. tenuis)

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Solitary mass in lymph node (North American Brugia)

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Masses in stomach/duodenum (Anisakis, Pseudoterranova) or small/large bowel (Angiostrongylus costaricensis)
○
Acute anisakiasis is a syndrome of immediate nausea, vomiting, and abdominal pain following ingestion of live worms from raw fish

•
Systemic manifestations of trichinellosis
○
Initial infection can present with diarrhea, abdominal pain, and vomiting

○
Release of larvae (1 week after infection) can lead to tissue edema, conjunctivitis, fever, myalgias, splinter hemorrhages, rashes, and have peripheral eosinophilia

○
Life-threatening symptoms include myocarditis, meningitis/meningoencephalitis, and pneumonitis

Laboratory Tests
•
Serological tests for antihelminthic antibodies can be helpful in confirming suspected clinical diagnosis but are available at limited number of reference laboratories

•
Stool examination for ova and parasites may be positive in larva currens but negative in all other entities

Treatment
•
CLM: Albendazole, ivermectin, or thiabendazole

•
LMP: Albendazole &/or surgical intervention if possible (accessible)

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LC: Ivermectin

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VLM: Albendazole with corticosteroids

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OLM: Albendazole &/or surgical intervention

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Trichinellosis: Albendazole/mebendazole

Prognosis
•
Vast majority of nematode zoonoses are asymptomatic or resolve completely with treatment

•
VLM and trichinellosis, when severe, can lead to mortality if not properly treated

Microbiology
Parasite Characteristics
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Ancylostoma : Migrating larvae up to 1 mm with bilateral double alae (wing-like projections on side of body)

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Angiostrongylus : 11-12 mm immature adults with dome-like lateral chords

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Anisakis/Pseudoterranova : 3rd- and 4th-stage larvae are 15-45 mm, have Y-shaped lateral chords, and a muscular trefoil-shaped esophagus

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Baylisascaris : Grow from 20 mm to 1.5 cm over time; smaller, thinner excretory columns and bilateral single alae

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Dirofilaria : 150-300 μm in diameter with large, broad lateral chords, and slender, paired muscle bundles; worms are often degenerated and inflamed

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Gnathostoma : 5-12.5 mm in length, 3rd-stage larva, head and cuticle with rows of spines, large lateral cords occupying most of body lumen

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Toxocara : 400 μm × 20 μm with large excretory columns and bilateral single alae

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Trichinella : 1.5-4.0 mm × 50-150 μm (adults), while encysted larvae are 1 mm in length and curled

Culture
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Plays no role in diagnosis of zoonotic nematode infections

Life Cycle
•
Ancylostoma cycle between mammals and environment and are species specific in their pathology
○
Filariform (infective) larva passes into human skin, fails to migrate into deep tissues, wanders aberrantly

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Angiostrongylus cycle between snails/slugs and rats
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Humans ingest food containing 3rd-stage larvae, which migrate through tissue and mature (incompletely) in meninges or gut

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Anisakis cycles between crustaceans, fish/squid, and sea mammals (dolphins)
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L3 larvae from undercooked fish enter human intestine, burrow aberrantly, and fail to mature or excrete eggs

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Baylisascaris cycles between raccoons and environment with other mammals as possible hosts
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Humans ingest embryonated eggs, larvae hatch and migrate through tissues, growing in size and wandering unrestricted, causing inflammation

•
Dirofilaria cycle between mammals and mosquitos
○
Humans are bitten by infected mosquitos, L3 larva migrates (usually a single worm) through tissue and usually dies, causing eosinophilic inflammation

•
Gnathostoma cycle between copepods, fish/frogs, seabirds, and pigs/dogs/cats
○
L3 larvae from undercooked fish enter human intestine, burrow aberrantly, and fail to mature or excrete eggs

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L3 larvae burrow out of gastrointestinal tract and can be found in skin, other organs, brain, and soft tissue

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Toxocara cycle in dogs (similar to Ascaris in humans), but may also pass through rabbits and other wild animals
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Humans ingest embryonated eggs accidentally, developing larvae migrate through tissues but cannot mature or excrete eggs

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Trichinella cycle between pigs (domestic) or bears (sylvatic) and rodents (both) with adult worms in intestine releasing larvae that move into muscle tissue to encyst
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Humans ingest undercooked pig or bear meat with cysts, worm completes its life cycle and releases larvae, which encyst in human skeletal muscle

Microscopic Pathology
Histologic Features
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Cross sections of living larvae or adult nematodes with variable neutrophilic/eosinophilic inflammation and necrosis
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Size of worm, location, and internal and external structures are key to speciation

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Eosinophilic granulomatous inflammation with central degenerated dead nematode structures
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Splendore-Hoeppli phenomenon and Charcot-Leyden crystals may be present

○
Identification of species may be difficult or impossible if structures are not intact

Ancillary Tests
Parasite Reference Testing
•
Although most zoonoses are self-limited and many do not require further treatment once removed surgical, complete speciation may be required for patient peace of mind

•
Specialized laboratories (e.g., Centers for Disease Control, Atlanta, GA) have morphological expertise available to speciate as well as possible

•
Molecular tests can be applied to classify existing or new species that may be found

Differential Diagnosis
Malignancy
•
Most common reason lung, soft tissue, and lymph node masses are biopsied is for fear of malignancy

Larva Currens (Strongyloides stercoralis)
•
Autoinfectious complication of a human infection with S. stercoralis (non-zoonotic)
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Worms are directly invading host from colon

•
Rapidly moving and has perianal involvement with more expansive urticaria

Tumoral Calcinosis
•
Collections of calcium may mimic calcified worm but should have limited inflammation and no eosinophils

Cysticercosis/Echinococcosis
•
Ruptured or remote cysts of either disease may appear as solitary masses in any site but should contain hooklets

Schistosomiasis
•
Calcified and granulomatous response around eggs may mimic worm cross sections, but granulomas are often exuberant and spines on eggs can be identified

Diagnostic Checklist
Clinically Relevant Pathologic Features
•
Clinical exposure history is often supportive of nematodes in tissue, but many cases may have no obvious exposure, requiring more careful analysis

Pathologic Interpretation Pearls
•
Fragments of material that do not appear to be of human origin with eosinophils should be evaluated as a possible helminth

28/11/2021

Hookworms
Canine hookworms include Ancylostoma caninum, A. braziliense, and Uncinaria stenocephala. Hookworm infection is one of the most common diagnoses in canine practice, and A. caninum is by far the most prevalent species involved. Ancylostoma eggs were identified in 19% of canine f***l samples collected from various locales in the United States [6].

Ancylostoma caninum infections can be acquired by vertical (transmammary) transmission, percutaneous invasion, or ingestion of infective third-stage larvae or paratenic hosts. In mature dogs with some acquired immunity, infective larvae may not develop directly into adults, but rather migrate to somatic tissues such as kidney and skeletal muscle, where they undergo prolonged arrested development [7]. These arrested larvae are most commonly reactivated by the hormones of pregnancy and lactation, and larvae are transmitted to suckling pups in the bitch’s milk. Although hookworm infection is observed in dogs of all ages, pups and juveniles are more likely to exhibit clinical signs of disease, including anemia, weakness, melena, anorexia, and weight loss or poor growth. As with most parasitisms, clinical signs are exacerbated by malnutrition, stress, or concurrent disease.

Hookworm disease (ancylostomosis) has been classified as four distinct syndromes which vary with the age, route of infection, or overall health status of the animal. In peracute ancylostomosis, suckling pups around 2–3 weeks of age die of severe anemia with no preceding clinical signs, due to overwhelming hookworm infections acquired through the transmammary route. Acute ancylostomosis involves slightly older or weaned pups that survive long enough to develop melena and signs of severe anemia. Again, transmammary infection is the usual route. The two remaining classifications of ancylostomosis occur in mature dogs that are either repeatedly exposed to L3 stages or are continuously reinfected with larvae activated from their arrested, somatic pools. Uncompensated ancylostomosis occurs when malnutrition or co-morbid disease render an animal incapable of managing hookworm insults through immunologic or general defense mechanisms. In contrast, no clinical signs are seen in dogs with compensated ancylostomosis, which is a term used to describe recurrent infections that are partially controlled, but not eliminated, by host mechanisms. Compensated ancylostomosis is typically recognized when f***l examinations after repeated treatments document the incessant reappearance of hookworm eggs.

Products labeled for treatment or removal of Ancylostoma caninum are the appropriate therapeutic choice for apparently healthy dogs or those with moderate signs of ancylostomosis (ie, compensated and uncompensated cases). Suckling pups with acute ancylostomosis require immediate and vigorous medical attention. Pyrantel pamoate/embonate is the preferred anthelmintic for this syndrome, due to its speed of activity and broad safety in debilitated animals. Ancillary medical management (eg, iron supplementation) is critical, but pups with acute ancylostomosis often make very dramatic recoveries once the immediate source of blood loss has been eliminated. By definition, anthelmintic treatment would arrive too late to salvage pups with peracute ancylostomosis, but surviving littermates should be treated promptly as for the acute syndrome.

Specific regimens of pyrantel pamoate have been designed to reduce the clinical impact of hookworm infections in suckling pups. These are described in greater detail in the section on Toxocara canis.

Current standards of care support the maintenance of all canine patients on some form of heartworm prevention, and all currently marketed Dirofilaria preventives are anthelmintics of the macrocyclic lactone (ML) class. Several heartworm preventive products have been developed in which the ML component is combined with other anthelmintics, including pyrimidines, to provide a broader spectrum of nematode control. Because most MLs also exhibit activity against hookworms, some of these combination products achieve higher efficacy against hookworms than either component used singly. For example, HeartGard Plus (ivermectin plus pyrantel pamoate) was more than 99% effective against adult Uncinaria stenocephala whereas pyrantel pamoate alone exhibited 93.4–96.3% efficacy [8]. Regular, monthly administration of such combination products reduces environmental contamination with hookworm eggs, and thereby reduces the risk of compensated or uncompensated ancylostomosis in mature dogs.

Uncinaria stenocephala is a less common hookworm of dogs that is most often acquired through ingestion of third-stage larvae (L3s). Uncinaria is more restricted in its geographic distribution than Ancylostoma caninum, occurring more frequently in Europe, Canada, and the northern tier of the United States. Uncinaria eggs were found in only 1.02% of canine f***l samples collected from around the United States [6]. Uncinaria ingests plasma proteins rather than whole blood, so clinical signs are primarily related to the gradual loss of vital nutrients. Ancylostoma braziliense is another fairly nonpathogenic hookworm of dogs that is limited to tropical and subtropical climates.

Routine Uncinaria and A. braziliense infections can be managed with approved anthelmintics containing pyrantel pamoate/embonate. Transmammary transmission does not occur with either species, so special regimens for suckling pups are not required. Some monthly heartworm preventives are also labeled for efficacy against U. stenocephala and A. braziliense (eg, HeartGard Plus). Regular control is advisable in endemic areas because both U. stenocephala and A. braziliense can cause a zoonotic condition known as cutaneous larva migrans [9].

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