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Home / Health & Science

Dog disease that drives goats, sheep crazy

Health & ScienceBy Gardy Chacha | Mon,Nov 08 2021 09:00:00 UTC | 4 min read


Chebo Chebunyo fetching water while dogs quench their thirst at Lokiwach water pan in Silale ward in Baringo county on January 30, 2019. [Kipsang Joseph, Standard]

Dogs are said to be man’s best friend, but this friendship exposes people to diseases like rabies. Besides rabies, there is also coenurosis, another dog disease that closely resembles rabies. The Maasai people even have a name for it: ‘Ormilo’.

Coenurosis is a zoonotic disease caused by the larval stages of Taenia species of tapeworms such as T multiceps and T serialis. It is very rare in humans. The world over, there have been about 30 confirmed cases of human central nervous system (CNS) coenurosis with the cases reported in Asia, Africa, the Americas and Europe.

The disease is also common in sheep and goats. Like human beings, goats and sheep get infected by consuming eggs – deposited with dog faeces onto grazing pasture or watering points.

“Dogs become infected by eating meat tissue of an infected intermediate host (containing a coenuri),” Mudoga says, adding the parasitic forms will then attach themselves onto the small intestine of the dog and develop into adult tapeworms.

“The adult tapeworms produce and release eggs inside the small intestines of the dog to start the lifecycle all over again,” Mudoga says.

Moses Nkiminis, a livestock owner says, ormilo in sheep and goats is not new in Kajiado and “it comes in waves: when it attacks, many goats and sheep just go mad. It may take months but eventually the animal dies.”

Humans become infected after accidental ingestion of eggs in food and water contaminated by faeces of the infected dog.

Eggs hatch in the intestine and release larval forms, which penetrate into the circulatory system; moving with blood until they lodge in a target organ: the brain, eyes and muscle tissues. Once lodged they develop into parasitic bodies called coenuri after about three months.

Mid last month, the Kajiado County government, in partnership with Action for Protection of Animals Africa (APAA), rolled out a campaign in which Jackline Koin, county Agriculture, Livestock and Fisheries executive, said, “We are targeting at least 4,000 dogs. We will be vaccinating them against rabies and deworming against ormilo.”

Dr Emily Mudoga, a veterinarian and a director at APAA, says though symptoms are similar, rabies – often transmitted to humans through bites of infected dogs – kills a victim quickly, “within two weeks”.

Mudoga says coenurosis is fatal too, but one might suffer for months and years before finally succumbing. The greatest challenge is that it is rare and a patient may never receive the correct diagnosis – suffering through their illness till death.

“Many a time it will go unnoticed. Usually, someone would suddenly suffer a form of blindness or a form of neurological disease that proves difficult to diagnose and treat. The disease can also be misdiagnosed as rabies, meningitis or even cancer,” explains Mudoga.

Volume 92 of the International Journal of Infectious Diseases cites the case of  a 38-year-old patient who was initially diagnosed with low-grade B-cell lymphoma after presenting visual disturbance and a headache. An MRI revealed a ring-shaped lesion in the part of the brain that interprets vision.

A biopsy was subsequently tested and a diagnosis of cancer issued. Chemotherapy was initiated and later a surgical resection of the lesion to completely remove it.

Pathological examination after surgery showed multiple tapeworm heads with hooklets and suckers. The patient had coenurosis.

According to Mudoga, coenurosis is always lurking in the shadows where sheep, goats and dogs share an ecosystem, and humans are always at risk.

“It is highly possible that we have patients who get coenurosis – especially in pastoralist areas – and die without ever being properly diagnosed. The disease is already with our livestock and as a zoonotic disease, it is just one step away from getting to humans,” he says.

The dog, for a pastoralist, is more than a best friend. “It is a personal assistant for a herder. It gives protection to the herd, especially against wild animals,” says Gideon Parsanga, an assistant chief in charge of Olo-Elelai sub-location in Bisil, Kajiado.

“We slaughter goats and sheep to mark ceremonies; to celebrate achievements; or to make merry. And of course our dogs eat the bits of meat that we throw away,” Nkimis said.

This then perpetuates the tapeworm’s lifecycle and hence its survival in the environment.

The best – and most cost-effective – way of eradicating coenurosis is by deworming dogs, Mudoga says, since when “you eliminate it in the dog then it cannot jump to man; neither sheep nor goats.”

Deworming is also the cheapest way of dealing with the parasite, considering “once a human is infected long-term treatment and surgery might be the only way to treat it. These can cost thousands or even millions of shillings. Deworming a dog, on the other hand costs, between Sh70 and Sh150 – the cost of buying a tablet.” Dogs need to be dewormed every three months (for working dogs) and every six months for pet dogs.

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