PUBLIC HEALTH IMPLICATIONS OF ABORTIONS IN FARM ANIMALS

1. Gajalakshmi

Fourth Year B.V.Sc. & A.H., Student

Veterinary College and Research Institute

Tamil Nadu Veterinary and Animal Sciences University

Tirunelveli 627358

Introduction

Abortion is the expulsion of the live or dead fetus of recognizable size prior to the end of normal gestation period. Abortion can occur due to a plethora of causes like nutritional, physiological, genetic, non-infectious causes (like heat stress, toxins, etc.,) and infectious causes among these, abortion due to infectious causes are important as they account for more than 50 % of the abortion. Infectious abortion can be caused by bacteria, viruses, protozoa and fungal agents, among these bacteria are more significant. Many of the bacterial agents causing abortions in farm animals are also known to cause disease in human beings, zoonotic significance. In this article the public health risk posed by abortion occurring in farm animals to the farmers, animal handlers, veterinarians and to the general public is highlighted.

Common organisms causing abortions in farm animals

Brucellosis: The members of the genus Brucella like B. melitensis, B. abortus and B. Suis are important cause abortion of in farm animals infection is acquired by ingestion of the organism present in aborted fetus, placenta and other fluids associated with abortion, and through contaminated feed and water. The aborted animals may shed a very high level of organism (1x 10⁸ to 1x 10¹³ colony-forming units (CFU)/ml or g of aborted materials) into the environment contaminating the animal shed. Abortion typically occurs in the late gestation period.

Campylobacteriosis: It is caused by Campylobacter fetus subsp. fetus but C. jejuni can also cause abortion especially in sheep. Infection usually occurs by ingestion of aborted tissues, vaginal discharge and feces (C. jejuni). C. fetus can be transmitted by venereal route through infected bull semen. It causes epizootic abortion in the late term with still birth/ weak young ones.

Chlamydiosis: The abortion caused by Chlamydophila abortus is popularly known as ‘enzootic abortion’ and is one of the most important cause of abortion in sheep and goat. The organism is transmitted by oronasal contact with aborted fetus, tissues and vaginal secretions. The abortion occurs in later stage of pregnancy and usually in primiparous animals but it will be continued to be excreted in subsequent pregnancies as well.

Coxiellosis: It is caused by Coxiella burnetii an obligate intracellular bacterial organism. The organism is transmitted between animals mainly by the bite of a tick vector or by direct contact with infected animals or its secretions, aerosol transmission is also possible. Abortion usually occurs in the third trimester of pregnancy and it may continue in the subsequent pregnancy as well.

Listeriosis: The pathogenic species under the genus is Listeria monocytogenes, which causes abortion in cattle sheep, goats and pigs. L. ivanoii can cause abortion in sheep. Transmission occurs mainly by ingestion of contaminated feed (poor quality silage). Abortion occurs in the third trimester, which is usually preceded by septicaemia.

Leptospirosis:The spirochetal organism Leptospira interrogans serovars are often associated with infection in animals.  Transmission occurs mainly through contact with urine of infected animals mainly rodents and the organism gains entry through both intact or abraded skin and mucous membranes. Abortion usually occurs in the last trimester of pregnancy.

Salmonellosis:It is caused mainly by Salmonella enterica subsp. enterica serotypes, cause systemic disease and abortion. Transmission occurs by feco-oral route through ingestion of contaminated feed and water. Abortion occurs in mid to last trimester of pregnancy, followed by retention of placenta and metritis.

Other bacterial pathogens associated with sporadic abortion in farm animals are ureaplasma diversum, truperella pyogenes ,yersinia pseudotuberculosis,  Mycoplasma, Fusobacterium necrophorum, Helicobacter bilis (Flexispira), Bacillus cereus, Bacillus licheniformis, E. coli, Staphylococcus aureus, Streptococci, Histophilus ovis, Mannheimia hemolytica, Pasteurella multocida, Arcanobacterium pyogenes, Histophilus ovis, Erysipelothrix rhusiopathiae, Francisella tularensis, Parachlamydia, etc.

Fungal agents causing abortion in farm animals include Candida, Mucor and Aspergillus. Many viral diseases are associated with abortion in farm animals include Bovine Viral Diarrhea virus, Blue tongue virus, Border Disease Virus, Rift valley fever virus, Akabane Virus, Nairobi Sheep Disease Virus, Herpes virus, Peste des Petits Ruminants virus, Cache valley virus, Wesselsbron Disease virus, Schmallenberg virus and others.

Among protozoan parasite causing abortion in farm animals the most important one is the Toxoplasma gondii, it can cause abortion in mid to late gestation. Cats act as definitive hosts for the parasite, which sheds the oocytes in its fecal matter. Transmission occurs by ingestion of oocytes contaminated feed and water. Other important protozoan parasite associated with abortion in animals are Neospora caninum, Sarcosystis, Tritrichomonas, Anaplasma, Trypanosoma species.

Zoonotic potential of the organisms

Among the list of pathogens causing abortion in farm animals discussed above, many are potent zoonotic agents especially bacterial pathogens. Thus, in addition to causing abortion and economic losses, these abortigenic agents can also infect the farmers and animal handlers causing serious life threatening diseases. The important pathogens that causes abortion in farm animals as well as associated with zoonotic infections are discussed below:

• Brucellosis in humans with the infective dose of even 10 to 100 organisms causes undulant fever, lymphadenitis ,arthritis, spondylitis and even abortion.
• Coxiella burnetii causes Q fever in humans, In infected patients clinical signs ranging from flu like symptoms to serious life threatening conditions like endocarditis, atypical pneumonia and repeated abortions are noticed. Only 1 to 10 organisms is sufficient to cause infection in humans.
• Chlamydiosis in human can also cause flu like illness, liver and kidney dysfunction and abortion in pregnant women who assisted during parturition in animals.
• Campylobacter jejuni in humans with the infective dose of 500 – 800 organisms can cause acute gastroenteritis, but secondary compilations like reactive arthritis, Guillain Barre’s syndrome can occur in a few fraction of the infected patients. fetus rarely causes disease in human beings like sepsis and abortion.
• Salmonella serotypes with infective dose of 1000 organisms can cause gastroenteritis with acute abdominal pain, certain serotypes can cause even abortion in pregnant women.
• Listeriosis in humans with 10 to 100 million colony forming units can cause septicemic disease, meningoencephalitis, conjunctivitis, abortions etc. Veterinarians who handle dystocia cases can have dermatitis with pustular and papular lesions on their hands.
• Leptospirosis is an important occupational hazard to butchers, vets and slaughter house workers. Signs of high fever, jaundice, abdominal pain, redness of eyes can be seen it can result in death due to multiple organ failure in severe cases.
• Toxoplasma gondii causes fetal abnormalities like hydrocephalus, mental retardation, chorioretinitis and encephalitis. Humans can also act as intermediate hosts for this protozoan parasite.
• Most viral agents that causes abortion in farm animals are not zoonotic and the fungal agents are only opportunistic pathogens.

Proper disposal of abortion content

The aborted materials and feed materials contaminated with aborted fluids should be properly collected and disposed by either burial or burning only. Before collection of the aborted materials, the tissues and the floor must be treated with appropriate disinfectants and for adequate contact time for effective disinfection. The materials should be collected only after wearing adequate personal protective gears like gloves, gumboots and facemask and goggles. The farm implements used for collection of aborted materials must be thoroughly disinfected after collection and disposal. The premises can be disinfected by burning straw with fuel. The shed where these aborted animals are maintained must be properly disinfected daily, as these animals continue to excrete the agents for prolonged period of time.

Preventive measures

• Culling of the aborted animal is must if the cause of abortion could be identified.
• Vaccination of the animals must be carried out properly when followed.
• Adoption of proper hygienic practices and bio security measures in the farm will be highly useful
• Regular testing of male animals used of semen collection should be carried out
• Maintaining of pregnant animals separately from that of other animals in the farm is important
• A separate calving pen should be maintained and closed herd policy can be followed.
• Purchase replacement stock only from known sources (accredited herds) and adoption of quarantine and testing measures should be followed.
• Proper record keeping system in the farm is must for early recognition of cases.

Conclusion

Abortion in farm animals occurs in many organized farms, when the rate of abortion exceed 2 to 5% measures to identify the cause of abortion for effective implementation of prevention and control measures in the farm. These abortions can also become serious public health threat especially to those who are in close contact with the farm animals or those who consume the products obtained from these animals. The farmers and those who are in close contact with farm animals must be made aware of the risk associated with these zoonotic agents causing abortion.

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