Abortion Storm in a Goat Flock with Raw Milk Sales and Human Illness
A 120-goat dairy flock in a village near Patiala has had 18 abortions in 3 weeks, mostly at 3-4 months of gestation. Two aborting does had retained placentas and a brownish vaginal discharge; three are lame. The farmer sells raw goat milk door-to-door and helps with deliveries barehanded. His two children, aged 7 and 10, have had fever and joint pain for 10 days. The village veterinarian submitted 20 serum samples; Rose Bengal plate test is positive in 9, including 5 aborting does. No culture or PCR result is available yet. The goats are not vaccinated against brucellosis. The farmer wants to treat the aborting does with antibiotics and continue selling milk.
1. What is the most likely cause, and how do you interpret the Rose Bengal plate test results? What further tests would you request and why?
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The abortion storm at 3-4 months, retained placentas, lameness, raw milk sale, and human fever with joint pain strongly suggest brucellosis, most likely Brucella melitensis in goats. The Rose Bengal plate test is a useful screening test, but it is not a confirmatory test. A positive result in 9 of 20 animals, including 5 aborting does, supports the diagnosis, but false positives can occur because of cross-reacting antibodies, and a negative result does not completely rule out infection in every animal. Request confirmation by ELISA or PCR on serum, placenta, fetal stomach contents, or vaginal swabs, and attempt culture from abortion material. Culture is the definitive proof but takes time and is hazardous. Test the whole flock, not only aborters, because latently infected goats can shed later. The children should be referred to a physician for brucellosis testing; their fever and joint pain should not be treated as a minor farm problem.
2. Set out immediate flock and public health actions for the next 30 days, including what to do with aborting does, milk, and the children.
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Immediately isolate aborting does and any positive reactors. Dispose of fetuses, placentas, and bedding by deep burial or incineration; do not feed them to dogs. Disinfect pens, boots, and equipment with an effective disinfectant. The farmer must wear gloves and wash hands after handling animals and aborting material; the barehanded delivery practice must stop. Stop all raw milk sales immediately. Milk from the flock should be boiled or pasteurised before consumption; pasteurisation means 63 C for 30 minutes or 72 C for 15 seconds, followed by rapid cooling. Inform the local veterinary and public health authorities because brucellosis is a zoonosis and a scheduled disease in many control programmes. Advise the family to seek medical attention for the children and for anyone with fever, sweats, or joint pain. For the flock, test and remove positive animals according to local policy, and do not introduce untested replacements. Antibiotic treatment of aborting does may reduce shedding but will not reliably eliminate infection, so it must not be presented as a cure.
3. The farmer asks whether vaccinating the whole flock now will stop abortions. Give a reasoned answer and a cost-effective control plan.
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Vaccination is not an emergency firebreak that will stop abortions in an already infected flock within days. Live B. melitensis Rev-1 vaccine is used mainly in young replacements, usually at 3-6 months of age, and it must not be given to pregnant animals because it can cause abortion. Blanket vaccination of pregnant does during an abortion storm is therefore unsafe and could worsen the problem. The cost-effective plan is test-and-cull of positive animals, strict separation of aborting does, hygiene, protected replacement rearing, and vaccination of young stock before first breeding. If culling all positives is economically impossible, the farmer must still stop raw milk sale and reduce exposure; partial culling with repeated testing is better than no action, but it will not eliminate infection quickly. Antibiotic treatment is not a substitute for control. Explain clearly that the family's health and the milk supply must be protected first, and that the flock will need repeated testing before it can be considered low-risk.