Schistosomiasis

Schistosomiasis is a common parasitic infection in cattle and rarely in other domestic animals in Africa and Asia. Most of the infections in endemic areas are subclinical.

High prevalence rates of subclinical infections cause significant losses in terms growth and productivity.

*Schistosome species of Veterinary Importance*

Prevalence of schistome species in India: S. spindale, S. nasalis, S. indicum and S. incognitum.

Intermediate host

Morphology

Schistosomes are called as blood flukes.
Unisexual – dimorphic trematode.
Female – long (12–28 mm) & slender.
Male – Comparatively small in length (9-22 mm) & having gutter-like groove (Gynaecophoric canal) in which female lodges at the time of copulation.
Cercariae – Furcocercous cercariae, tail is forked.
Egg – 100–500 µm long and spindle shape without operculum.
Some species having lateral spines.

Developmental stages

Redia and metacercariae stages are absent.
Two generation of sporocysts (I and II).
Immature schistosomes is called as Schistosomula.

Epidemiology

Cattle is highly susceptible than buffalo, sheep and goat.
Older bovines (>3 years) are highly susceptible.
Infection also occurs in 5-6 months old calves.
Both male and female animals are equally affected.

Transmission

Horses and cattle may get infection when standing in shallow infected water source of dam or river.
Buffalo get infection while wallowing in the infected water sources.
Slow moving water favour the entry of cercariae into body of animal.
Consumption of water contaminated with cercariae.
Highest rainfall (Season: Sepember to October).

Life Cycle

Pathgenesis

Acute intestinal syndrome
Chronic hepatic syndrome

Nasal schistosomiasis (Pseudotubercle or Actinobody formation or Snoring Disease)

Clinical signs

Cattle

Rhinitis, mucopurulent discharge, signs of coryza, sneezing and dyspnoea and snoring respiration.
Adult parasite causes dilation and thrombosis of vein.
Nasal mucosa studded with small granulomas and small abscess containing eggs.
In chronic cases– proliferation of nasal epithelium and fibrous tissue formation may occur.
Space occupying lesion in nasal septum results in breathing difficulties leads to snoring respiration.

Buffalo

Pin sized eruption and congestion of nasal mucosa is called as Actinobodies.
Diarrhoea, sometimes blood stained and contains mucus.
Anorexia, thrust and emaciation.

Clinical signs in other schistosome species

Migration of large no. of worms through lung causes temporary cough.
Profuse watery diarrhoea or dysentery.
Dehydration and anorexia.
Anemia and hypoalbuminemia.
Decrease in production and loss of weight.

Immunity

Natural immunity: it is occur in cattle after infection.
Artificial immunity: Administration of irradiated Schistosomula of S. mattheei and S. bovis S/C or I/M to cattle or sheep induce protection greater than 60% against schistosoma infection.

Clinical pathology

Anemia, Eosinophilia, hypoalbuminemia, hypergammaglobulinemia.
Dyshaemopoisis and expansion of plasma volume.

Diagnosis

Based on clinical signs.
Detection of schistosome sp egg in faecal sample examination.
Detection of schistosome sp egg in nasal washing.
Measuring cell mediated immune response.

Differential diagnosis

Rhinosporidiosis
Tumour

Treatment

Tartar emetic- 2 mg/kg
Sodium antimony tartrate– 1.5 mg/kg twice a day for 2 days.
For cattle praziquantel at 25 mg/kg is highly effective but, it require two treatment at 3-5 weeks apart.
Trichlorophon- 30–40 mg/Kg three doses.
Niridazole: Sheep – 100 mg/Kg for 3 days, Pig: 25-30 mg/kg.
Praziquantel: Sheep and goat – 60 mg/kg.

Control

Management practices and snail control similar to that of Amphistomiasis and Fasciolasis.
Biological control Schistosomes larvae.
Larval stages of Echinostoma spp. is used as predatory on schistosome larvae within the snail intermediate host.
Microsporidial protozoa – Nosema eurytremae can cause extensive damage to intramolluscan stage of schistosomes.
Avoid contact with infected water sources.

Cercarial dermatitis (Swimmers itch or Clay-diggers itch or Hunters itch or Rice-Paddy itch)

Cercarial dermatitis (Swimmers itch or Clay-diggers itch or Hunters itch or Rice-Paddy itch) is caused by skin penetration of cercariae of non human schistosomes (Avian schistosomes Trichobilharzia sp. and Austrobilharzia sp) and animal Schistosomes (Heterobilharzia spp.) in man.
Initial exposure to cercariae causes a mild erythema and edema, but repeated exposure causes severe pruritis and papular or pustular eruptions.
Treatment: Application of benzyl benzoate over the body and antihistaminic therapy.
Prevention: Wearing protective clothing while working in the infected water sources.