Hookworm and Toxocara Infections
Hookworm (Cutaneous Larva Migrans)
Larvae of animal hookworms cause this condition in humans. Found in animal feces and contaminated soil, they penetrate human skin causing a crawling eruption. Humans are not the definitive host; larvae migrate aimlessly in tissues and do not complete their life cycle.
Causative Agents
- Ancylostoma caninum (dogs): More common in tropical and subtropical countries. Potential zoonosis: cutaneous larva migrans.
- Uncinaria stenocephala (dogs): Increased prevalence in Chile (temperate and cold climates). Blood-sucking, oral cavity, dorsal curvature, copulatory bursa.
Characteristics
Life cycle similar to A. duodenale, but depends on the host exposing skin to filariform larvae.
Transmission
Skin contact with larvae.
Factors
- Presence of pets (contaminated environment)
- Irresponsible pet ownership
- Children playing with soil
- Going barefoot or exposing bare skin on the ground
Pathology / Symptoms
Intraepidermal Migration
Itching, burning, or pain. Commonly affects soles of feet, palms of hands, buttocks, etc.
Lesion Characteristics and Evolution
Itching, red papules at the invasion site, erythematous vesicular injury, serpiginous tunnel (advancing 2 to 5 cm per day), may develop pyoderma (secondary infection).
Diagnosis
Clinical presentation, observation of the lesion.
Treatment
- Albendazole: 400 mg/day for 3 to 5 days
- Thiabendazole: 25 mg/kg/day every 8 hours for 7-10 days
There is no spontaneous cure (takes weeks or months).
Prophylaxis
- Health education
- Responsible pet ownership
- Veterinary medical monitoring
- Periodic deworming
Visceral Larva Migrans (Toxocara Canis)
Found in the small intestine of dogs. Transmission can be transplacental. Definitive Host (DH): Dogs.
Location
- Adults: Small Intestine
- Larvae: CNS, Muscle (Mm), Myocardium (M), Retina (R)
Male: ~10 cm, Female: ~18 cm.
Life Cycle (in Humans)
When humans ingest infective eggs, gastric juices digest the eggshell, releasing larvae. Larvae migrate from the intestine because humans are not the definitive host. They travel to various organs and tissues, where the body’s immune response attempts to contain them by encapsulation.
Larva Migration Destinations
Larvae can migrate to different tissues, causing two main forms:
- Visceral Larva Migrans (VLM): Affects internal organs.
- Ocular Larva Migrans (OLM): Also known as Ocular Toxocariasis. Typically affects only one eye.
Cycle elements: Dog, Human, Larva (Temperature, Feces, Soil, Shade).
Pathology in Humans (VLM)
Lesions
Inflammatory granuloma: Eosinophils, Lymphocytes, etc. Frequently found in lungs, liver, CNS, ocular tissues.
Population at Risk
Pediatric population (visceral form).
Symptoms
- Benign Form: Eosinophilia, hepatosplenomegaly.
- Other Symptoms: Asthma-like symptoms, lymphadenopathy, myalgia.
- Severe Form: Pneumonitis, nephrosis, brain injuries, etc.
Ocular Form (OLM)
- Unilateral loss or alteration of visual acuity
- Strabismus
- Red eye
- Leukocoria (white pupil reflex, can mimic retinoblastoma)
Epidemiology
Worldwide Distribution
Puppies between 2 and 3 months of age are highly susceptible. Prevalence data varies:
- Canines: 6.2%
- Felines: 50%
- Human: 2.6%
- Parks: 20%
Human Prevalence in Chile (1985)
8.8% overall. 8.3% in healthy adult population. Majority were male children aged 7. In one town, 20% of asthmatic children and 25% of patients with eosinophilia were affected.
Infectivity Distribution in Animals, Parks, and Humans (Chile)
- Canines: 15.2% (1955) and 40% (1979). >1 year old: 23-40%. Conception: 6% in feces.
- Other Animals: Cats 25-50% (Santiago), 20% (2002).
- Parks: 10.7% (1986) and 71.7% (1996). Santiago Parks: 10.7% (eggs/gram of soil).
Diagnosis of Toxocariasis
Canines and Felines
Anamnesis, clinical symptoms, macroscopic exam (stools and vomiting). Migratory phases are difficult to diagnose.
Humans
- VLM: Clinical presentation, laboratory tests (hypereosinophilia), ELISA.
- OLM: Specific ophthalmic review (fundus exam), ELISA, routine eye exam, ultrasonography.
Treatment of Toxocariasis
Canines and Felines
Symptomatic treatment and use of anthelmintics:
- Dichlorvos
- Febantel / Pyrantel Pamoate
- Fenbendazole
- Pyrantel Pamoate
- Ivermectin
- Mebendazole
- Levamisole
- Piperazine Citrate
- Nitroscanate (among others)
Humans
Symptomatic treatment. Use of antiparasitic agents and corticosteroids in VLM.
Prophylaxis
General Measures
- Treatment of female dogs and pups
- Remove fecal material promptly
- Clean kennels (hotels, breeding facilities)
Veterinary Measures
- Continuous deworming programs
- Community education
Medical Measures
- Health education for the public