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Schistosomiasis in Cattle
Definition
Parasitic disease of cattle.
Produces visceral or nasal disease.
Caused by genus Schistosoma, family Schistosomatidae.
Hosts
Cattle primarily.
Rarely seen in other domestic animals in Africa and Asia.
Adult worms parasitize vascular system of vertebrates.
Ruminants infected by skin penetration or orally.
Geographic Distribution
Common in Africa and Asia.
Occurrence depends on intermediate snail hosts, infection level, water contact.
Specific species distributions:
S. mattheei: Southeastern Africa.
S. bovis: Mediterranean, Middle East, much of Africa.
S. curassoni: Parts of West Africa.
S. spindale: India, Sri Lanka, SE Asia.
S. indicum: Indian subcontinent, Bangladesh.
S. nasale: India, Sri Lanka, Bangladesh, Myanmar.
S. incognitum: India, Thailand, Indonesia.
S. japonicum: Far East.
Organism (Schistosoma)
Genus: Schistosoma.
Family: Schistosomatidae.
Adults in vascular system.
Dioecious (male carries female).
19 species naturally infect animals; 8 significant in ruminants.
Species differentiation by egg morphology (size, shape, spine).
Egg morphology examples: spindle (S. bovis/curassoni/mattheei), elongated (S. spindale), boomerang (S. nasale), oval with rudimentary spine (S. japonicum).
Hybridization: Interspecific (S. bovis x S. curassoni). Natural human x ruminant (S. haematobium x S. mattheei/bovis/curassoni). Results in intermediate egg morphology. Hybrids may have enhanced infectivity/fecundity/growth and influence pathology/drug sensitivity.
Life Cycle, Transmission & Epidemiology
Adults live in mesenteric/hepatic veins (except S. nasale in nasal veins).
Feed on blood, produce spined eggs.
Eggs in feces need water to hatch miracidia.
Miracidia invade water snails (Intermediate Hosts: Bulinus, Biomphalaria, Indoplanorbis, Lymnaea).
Develop in snail to cercariae.
Cercariae leave snail, swim freely.
Ruminants infected by skin penetration or orally.
Cercariae become schistosomula, travel to predilection sites.
Prepatent period: 45-70 days.
Transmission linked to presence of infected snails and water contact frequency.
S. nasale transmission via percutaneous penetration from infected Indoplanorbis snails.
Epidemiology:
High prevalence (40-70%+) in favorable areas.
Most infections subclinical in endemic areas.
High prevalence of subclinical infections causes long-term losses (growth, productivity, susceptibility to other diseases).
Occasional clinical outbreaks in young/adults with heavy primary infections.
Acquired immunity exists (mainly suppresses worm fecundity).
Partial protection against reinfection occurs.
Acquired resistance regulates infection intensity.
Hybrids' increased host range/distribution impacts transmission.
Clinical Findings & Lesions
Disease can be visceral or nasal.
Severity varies (subclinical to fatal).
Visceral Schistosomiasis
Mostly subclinical in endemic areas.
Chronic infections cause significant herd losses (less recognized effects).
Clinical signs (in outbreaks): diarrhea, weight loss, anemia, hypoalbuminemia, hyperglobulinemia, severe eosinophilia (after egg excretion).
Severe cases: rapid deterioration, possible death (within months).
Less affected: chronic disease, growth retardation.
Adult flukes in portal, mesenteric, intestinal veins.
Main pathology from eggs:
Intestinal form: passage through gut wall causes lesions.
Hepatic form: granulomas around trapped eggs.
Hepatic lesions: medial hypertrophy/hyperplasia of portal veins, lymphoid nodules/follicles, periportal fibrosis (chronic).
Intestinal lesions: extensive granuloma formation, petechiation/hemorrhage, discolored blood in lumen.
Vessels dilated/tortuous.
Vascular lesions in lungs, pancreas, bladder possible in heavy infections.
Nasal Schistosomiasis
Associated with cauliflower-like growths on nasal mucosa.
Causes partial nasal obstruction, snoring sounds.
Hemorrhagic/mucopurulent nasal discharge common.
Adult flukes in nasal mucosa blood vessels.
Main pathology from eggs: cause abscesses.
Abscesses rupture, releasing eggs/pus, leading to extensive fibrosis.
Large granulomatous growths obstruct passages, cause dyspnea.
Reduced market value due to snoring disease.
Diagnosis
Based on clinical signs, egg identification, serology.
Signs/history insufficient for visceral form.
Methods:
Egg Detection:
In feces.
At necropsy: mesenteric veins (adults), scrapings/crushed tissue (eggs).
Microscopic examination of stained smears or tissues.
Low fecal egg excretion in chronic cases.
Quantitative miracidial hatching techniques are more sensitive and show egg viability.
Serology: Useful for detecting previous infection.
Molecular Analysis: Identify organism, phylogenetic relation. PCR for Schistosoma DNA for higher specificity/sensitivity.
Treatment and Control
Treatment
Compounds: Anthiomaline or praziquantel.
Praziquantel (25-30 mg/kg PO) highly effective for visceral form. May need 2 doses.
Rarely treated in some areas for practical/economic reasons.
Mass treatments used in China (reservoirs for human infection).
Used in India for cattle brought for veterinary attention.
Triclabendazole (20 mg/kg) adulticidal effect against female worms.
For nasal schistosomiasis: Anthiomaline injection (15 mL IM). Reduces granuloma size, snoring. Repeated weekly if needed (2-3 injections usually effective).
Control
Most effective: Prevent animal contact with parasite/water.
Fencing dangerous waters, supplying clean water. (Difficult with nomadic management).
Destroy snail intermediate hosts: Chemical, biologic methods, mechanical barriers, traps.
Ecologic measures against snails: drainage, water weed removal, increased water flow. Also helps control other trematodes (Fasciola gigantica, paramphistomes).
Avoiding grazing near snail-infested areas.
Periodic deworming in bullocks.
Treatment at the early stage of infection.
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