Haemonchosis is an important disease of ruminants and exerts greatest economic effect in goats in those countries where there is good summer rainfall. It is characterized clinically by server anemia, chronic wasting and anasarca.
Reason for Haemonchosis in goats
Sheep, goats and cattle are affected by Haemonchus species, which is closely related to other trichostrongylids of ruminants. Of different species, H.contortus is most commonly found in sheep and goats.
Spread of Heamonchosis in India
The epidemiology of haemonchosis is largely determined by the high fecundity of the female worms and the speed with which infective larvae can develop in warm and humid conditions. Therefore, when conditions are favourable, large numbers of infective larvae can accumulate very rapidly on pasture. The greatest economic impact of haemonchosis is seen in goats and sheep in India, especially where there is good summer rainfall. However, since high humidity, at least in the microclimate of the faeces and the herbage, is also essential for larval development and survival, the frequency and severity of outbreaks of disease are largely dependent on the rainfall in any particular area. In certain areas of the tropics and subtropics, the survival of parasite is also associated with the ability of H. contortus larvae to undergo hypobiosis which occurs at the start of a prolonged dry season and permits the parasite to survive in the host as arrested L4 instead of maturing and producing eggs.
Blood sucking parasite of goats – Real harm to goat sector is parasitic diseases
The vigorous blood sucking by larva and adults is the main differentiating feature of pathogenesis of H. contortus from other parasites of goats. Each worm ingests about 0.05 ml of blood per day and thus an animal with 2500 H. contortus may lose about 125 ml blood daily. Average weight of goat in India is around 22kg and it contains hardly 2000ml blood. When animal loses 125ml blood daily it will cause loss in production which can be estimated through loss of weight. In acute haemonchosis, anaemia is noticed in about two weeks after infection and it is characterized by progressive and significant fall in Red blood cells (oxygen carrying cells). However due to continuous loss of iron and protein into the gastrointestinal tract and increasing inappetance, the bone marrow eventually becomes exhausted and the packed cell volume falls further before animal die. In goats, consequent agalactia (loss of milk production) may result in death of suckling lambs. The kids on a high protein diet can better withstand H. contortus infection. Higher protein intake elicits an effective immune response and thereby, kids are able to tolerate and compensate the blood losses associated with the infection better. However, high energy and protein diets exposed the kids towards Enterotoxemia and consequent death. So, it will be better if kids are vaccinated against ET at 7 day.
Important points to be remember
- The disease causes heavy losses due to deaths and reduced production. In per acute cases goats and sheep dies suddenly from heamorrhagic gastritis.
- A cute haemonchosis is characterized by anaemia, variable degree of swelling, of which submandibular form and ascites are most easily recognized.
- There is lethargy, dark coloured faeces and falling of wool in case of sheep.
- Diarrhoea is not a general feature of the disease.
- Chronic (long course) haemonchosis – with less no. of worms, is associated with progressive weight loss and weakness and severe anaemia or gross oedema is not noticed.
- The development of anaemia and hypoproteinaemia depends on the erythropoietic capacity of the animal, availability of the iron reserves and nutritional metabolized reserves of the host.
- Faecal egg counts may at times be less than 200 EPG. Prolonged chronic cases reveal lethargy and muscular weakness, paleness of mucosae and conjunctivae and antisera particularly under the lower jaw and to a lesser extent along the ventral abdomen.
- Heavy infection occurring in summer may not manifest clinically until winter when the nutritional status becomes poor.
- FAMACHA TEST – Field test has been developed to detect the worm load in intestine. Originally compiled by the Faculty of Veterinary Science, University of Pretoria, the Onderstepoort Veterinary Institute -South Africatitute, the Worm Workshop of the South African Veterinary Association, and Intervet South Africa, with the support of the Food and Agriculture Organization of the United Nations, the National Wool Growers’ Association and the National and Provincial Departments of Agriculture in South Africa.
Findings in dead animals
In animals died of the disease, gross necropsy lesions include severe anaemia, gelatinization of fat deposits, general swelling of the body and presence of large numbers of readily visible parasites in the abomasum. The mucous membranes and skin become pale while blood has a watery appearance. The internal organs are also markedly pale. The stomach wall becomes hyperemic and blood clots may be present in the mucosa. Small ulcerations at the sites of adult worms attachment are noticed. The abomasal contents are of distinct brown colour due to the presence of free blood.
Diagnosis
The history and clinical signs are usually important for the diagnosis or acute infection. The faecal egg counts are necessary to know the severity of infection. This parasite is a prolific egg layer and the faecal egg count may be up to 10,000 in severe cases.
The faecal worm counts and haemoglobin levels are also correlated. The diagnosis of chronic haemonchosis is more difficult because of the concurrent presence of poor nutrition and confirmation may have to depend on the gradual disappearance of the syndrome after anthelmintic treatment.
Other common causes of anaemia are fasciolosis, eperythrozoonosis and cobalt and copper deficiencies. Diarrhoea is more prominent in trichostrongylosis and coccidiosis. In calves, haemonchosis should be differentiated from babesiosis, anaplasmosis, coccidiosis and hookworm infestation.
Drugs used to treat Heamonchosis (parasitic diseases) in goats
In acute cases (sudden occurrence) Commonly available anthelmintic drugs can be successfully used to treat parasitic diseases.
Piperazine adipate, NILZAN, ALBOMAR, BANMINTH forte, NILVERM, FENCUR,XYCLOZ closantel.
Chronic hacmonchosis can also be managed similarly. If possible, the new pasture should have a good nutritional value. Closantl, disophenol and other narrow spectrum products exert a persistent protective effect in goat up to a period of 4 weeks. Organophosphate anthelmintics are available in some localities for use against the resistant strains. Resistance in H. contortus strains to localities for use lavamisole, morantel, ivermectin, and closantel has been reported and multiple resistances to two or more of these chemicals is common in some areas.
Prevention and control
In areas here larvae remain over winter on pasture, they infest kids in early spring. Treatments may be needed in spring and early summer to prevent the accumulation of infection in the sheep. If no routine control is practiced and pasture contamination becomes high, the animals should be dewormed and moved to clean grazing areas. If it is not possible then use of anthelmintic such as FENCUR or XYCLOZ or NILVERM should be practiced. Frequent use of broad-spectrum anthelmintics can lead to the development of resistance. Lambs can be given any of these drugs when they are about 12 weeks of age and the drug should be repeated after 12 weeks again.
Vaccination is another method for preventing the infection and considerablc progress has been made in this direction. Young lambs can be protected by the passive transfer of colostral antibodies from vaccinated ewes. An experimental molecular vaccine based on the H. contortus gut membrane antigen has been shown to reduce faecal egg counts by 90% and worm burden by 72-80%.
In poor farming regions, routine use of modern anthelmintics or vaccination may be expensive and therefore, alternative suitable methods are required. The dietary manipulution may be possible to ensure optimum intake of cobalt and molybdenum. Section for genetic resistance may also he attempted.