Abortion Causing Protozoan Parasites in Ruminants

Alok Kumar Singh1#, Amit Singh2, Shalini Tiwari3,Snigdha Shrivastava4and Ravi Kumar Khare5

1,5Department of Veterinary Parasitology, College of Veterinary Science & A.H., Rewa
2Department of Veterinary Parasitology, ANDUAT, Kumarganj, Ayodhya
3B.V.Sc & A.H., Students, College of Veterinary Science & A.H., Rewa
4Ph.D. Scholar, Department of Veterinary Medicine, COVSc & A.H., Rewa

Protozoan parasites causes serious disease in affected animals and may lead to poor growth, loss of body weight, reduced milk and wool production. Some other protozoan diseases which are usually not fatal but cause ill health and debility, reduce the productivity of the affected animals. The impact of the protozoa on their hosts causes infertility in livestockwhich may lead to severe economic losses. The most deterrent to efficient animal production and herd profitability is pregnancy loss, of which protozoan infections can be a possible cause.

There are several protozoan parasites that causes abortion in the case of ruminants.

1)Tritrichomonas foetus:

It is a veneral disease of cattle, there is early pregnancy(one to two week of gestation) loss and abortion and pyometra leading to significant infertility. The organism causes a genital disease called ‘bovine trichomonad abortion’ in cattle. This disease has been reported from West Bengal, Bihar, Rajasthan, Jammu region and Orissa. Neither the cow nor the bull appears ill despite ofthe infection, the animal may conceive normally, retains the calf up to full term and gives birth to normal healthy calf. Abortion usually occurs 8-16 weeks after conception.Thefoetus and membranes frequently pass unnoticed and this may lead to the assumptions that there has been an irregular oestrus cycle. Abortions beyond six months of pregnancy are rare.

Abortion is caused by with detachment of the placental membranes and death of the foetus between 8 to 16 weeks after the infected service. Uterine discharge and a series of irregular heat period are some other signs. Endometritis occur if the foetus and membranes does not pass out of the body completely.Trichomonas organisms are confirmed by demonstratimg from litres of white uterine fluid specimen.If there is absence of bacterial contaminaton this fluid is odourless. There is associated anoestrus and the animal appears apparently pregnant during this period.

  • Dimetridazole is effective drugs when given parenterally @50 mg/kg b.wt.

2) Sarcocystis cruzi: Sarcocystis cruzi is the most pathogenic species in cattle and sarcocystosis is  caused by single-celled  coccidian protozoan parasite.Clinical signs includes fever, anorexia, loss of weight, hair loss, weakness, muscle twitching, prostration, abortion, reduced milk yield, hypersalivation, neurologic signs, and death, depending on the isolate and the number of sporocysts ingested. Doses of 5 million or more sporocysts are fatal.Cows may abort, and milch cows may show reduced milk yield.

3) Sarcocystis tenella: This species is highly pathogenic for lambs. It can cause anorexia, weight loss, fever, anaemia, loss of wool, abortion, premature birth, nervous signs, myositis, and death, depending on the number of sporocysts ingested.Infected pups showed mild inappetence and diarrhoea.

4)Sarcocystis capracanis: S. capracanis is the most pathogenic species in goats. It causes fever, weakness, anorexia, weight loss, tremors, irritability, abortion, and death, depending on the number of sporocysts ingested. Anorexia and diarrhoea were reported in pups experimentally fed sarcocysts of S. capracanis.

5) Toxoplasma gondii:

Sheep:T. gondii causes abortion in ewes of all age groups which acquire infection during pregnancy.  T. gondii organisms have been recovered from diaphragm, psoas muscle and from the brain.At the time of abortion the ewes are clinically normal. Lambs may be mummified, macerated, aborted, stillborn, or may be born weak or die within a week of their birth. The ewes which abort return to heat and conceive normally.

Goat: The parasitaemia develops within one week after infection, and T.gondii encysts in the subsequent week.signs may be fever, anorexia, diarrhoea and respiratory distress and goat may die of enteritis. Abortion may occur at any part of time within 3 weeks of the infection in all age groups. T. gondii can cause early embryonic death, mummification, abortion, still birth, or birth of weak kids in goats. The organisms can persist in the tissues of goats for life. In the thigh muscle, heart, diaphragm, liver, kidneys,brain, liver and muscle cysts are found. Lesions are more pronounced in the foetus infected in the first half of gestation. There are no specific lesions.

  • Sulphadiazine and pyrimethamine are two drugs widely used for therapy of toxoplasmosis. Both these drugs act synergistically by blocking the metabolic pathway involving p-aminobenzoic acid and the folic-folinic acid cycle respectively. These are well tolerated but sometimes, thrombocytopenia and/or leukopenia may develop. These effects can be overcome by giving folinic acid and yeast. Since sulfa compounds are excreted within few hours of administration, treatment has to be administered in daily divided doses usually for several weeks or months.

 Other drugs,are diaminodiphenylsulphone (DDS), spiramicin, chlorinated lincomycin analogues, lasalocid, monensin, piritrexim, and roxithromycin. Clindamycin is also reported to be effective against T. gondii but may cause ulcerative colitis.

Recently, ‘Toxovax’ a new live vaccine, has been introduced to protect ewes intended for breeding, against T. gondii infection, and to check embryonic death and abortion.

(6)Neospora caninum:Itcauses serious disease in cattle. N. caninum parasite transmitsmost efficiently transplacetally in cattle. Postnatal transmission also occur due to the ingestion of sporulated oocysts of N. caninum thus causing abortion in bovine herds .The major economic loss due to neosporosis is reproductive failure in cattle and foetal lossis the direct harm to economy. Besides, itmay effect milk production. Neonatal calves may also become infected by the ingestion of colostrum and milk containing tachyzoites.

(7)Anaplasma marginale:  The primary mode of transmission of this organism is by ixodid ticks which are species of Boophilus, Dermacentor, Hyalomma, Ixodes and Rhipicephalus. Argas and Ornithodoros also act as vectors. There may be mechanical transmission of A. marginale by blood sucking flies, viz., tabanid flies, deer fly, Stomoxys and mosquitoes. The disease may also be transmitted during surgical operations such as dehorning, castration, vaccination, blood sampling etc. The disease is found in cattle and buffaloes in India.

Generally, A. marginale organisms occur inside the erythrocytes as round, filamentous, oval or disc like. In nearly 80 percent cases, the organisms are seen located near the margin of the erythrocytes.

Clinical anaplasmosis is mostly seen in cattle above 18 months of age and is less frequent in younger animals. Incubation period varies with the mode of infection and the amount of infective stages injected. After tick–borne infection, it may be between 15-36 days (av. 26 days) while, after inoculation of the infected blood, it may be 1-5 weeks.

Symptoms include fever which may fluctuate with irregular periods, anorexia, pale/jaundiced mucous membranes particularly after the acute phase passed. Haemoglobinuria is absent. In per acute cases, there is sudden onset of high fever, anaemia, icterus, severe dyspnoea and death often within 24 hours in adult dairy cows. In chronic cases, there is severe anaemia and the animals become susceptible to other infections. There is loss of milk production in cows. There may be abortion in pregnant cows. In sheep and goats, disease is subclinical but for, in few cases, a severe anaemia similar to that of cattle. In experimental infection in lambs, fever appears after 15-20 days of infection followed by constipation or diarrhoea pale eyes and severe anaemia.

  • Tetracycline @ 6-10 mg/kg bodyweight is effective.
  • It is more usual to give 3 such daily injection.
  • Imidocarb and berenil are also used in the treatment.
  • Supportive treatment includes slow administration of blood transfusion.