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Carnivores Spread Distemper to Lions
New research shows that dogs are no longer the primary source of a disease that has infected and killed lions in Tanzania. Canine1 distemper now appears to be spread mostly by other carnivores, such as hyenas2, jackals and foxes.
In 1994, about 30 percent of the lions in Serengeti National Park died from – what was then – a mysterious neurological disease. It was later identified as canine distemper.
Veterinarian Felix Lankester said that “the dynamics3 of the distemper virus are extremely complex….Canine distemper is an infectious disease that’s caused by a virus called the canine distemper virus, which is in the same family as measles4 and rinderpest. So it’s a viral infection that affects dogs, commonly, but it can also infect wild carnivore species.”
In the ’94 outbreak, domestic dogs were responsible.
“There are lots of domestic dogs living in human communities around the national park. And there’s one particular area in the northwest of the national park where there’s a lot of people and quite a high density5 of dogs,” he said.
Since then, blood samples of various animals have been tested for signs of canine distemper.
“What we found is that there have been peaks in antibodies in the lion population. So the virus has come into the population since the 1994 outbreak. And what we were expecting to see is that those peaks would be related to peaks of antibodies in the domestic dog population – showing that the domestic dog population had an outbreak of distemper and that that would then be followed by an outbreak in the lion population,” Lankester said.
However, the antibody peak in lions did not correspond to a peak in domestic dogs. So, the dogs were not the primary source.
Lankester said the canine distemper virus is spread by physical contact.
“Social contact within a social group, like a lion or domestic dog bite -- dogs licking each other or grooming6 each other, fighting, mating. But it’s also spread from species to species we think at points of contact like when carnivores scavenge at a carcass and you get multiple species at that carcass. And they might fight with each other or they might eat a bit of meat or bone that’s already been contaminated with the saliva7 from one animal. That is an area where disease can move from one species to another.”
And animals eat one another. Hyenas, for example, may prey8 on domestic dogs around Serengeti National Park. However, there hasn’t been much evidence the canine distemper virus has affected9 hyenas much. Sometimes the virus can even pass through a lion population with few if any symptoms.
“It’s a very curious disease. Sometimes it causes outbreaks that are clinically apparent with lots of death and diseased animals. And other times it passes through and you don’t see any symptoms whatsoever,” Lankester said.
The canine distemper, he said, virus now may be established in the wild among several carnivore species rather than the domestic dog population. A big reason for that may be domestic dogs around Serengeti National Park are being vaccinated10 for distemper, rabies and the parva virus.
“It’s probably reduced the intensity11 of transmission of the virus into the national park and into lion populations. But what we’re seeing is that it hasn’t prevented the lions from becoming infected completely. And so there is clearly some other transmission going on that the vaccination12 campaign has not managed to prevent.”
Lankester said evidence of it spreading into other animals can be found in Eastern Russia where Siberian tigers are now becoming infected and dying.
“There’s a lot more work to be done to understand really how the virus is working. How it’s changing. How it’s mutating. How new species are becoming infected with this and what the implications are of those species becoming infected,” he said.
Lankester is a clinical assistant professor at the Paul G. Allen School for Global Animal Health at Washington State University. However, he’s based full time in Arusha, Tanzania. While research continues into canine distemper, he also focuses on rabies, which is widespread in Africa and Asia.
“Rabies is what we call a neglected tropical disease. It’s causing fatalities13 all around the world. Every year, approximately 69,000 people are dying of rabies. Almost half of those are children under the age of 16. As we all know, it’s a horrific disease. It’s one of the most lethal14 diseases known to mankind, which means once somebody becomes infected and symptomatic they nearly invariably die,” he said.
He said in Africa and Asia the disease is nearly always transmitted by domestic dogs. It’s entirely15 preventable with vaccines16. Lankester and his colleagues are campaigning for funds to establish national canine vaccination campaigns to eliminate rabies on those continents. In the United States, the rabies reservoir is usually wild animals, such as raccoons and skunks17.
1 canine | |
adj.犬的,犬科的 | |
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2 hyenas | |
n.鬣狗( hyena的名词复数 ) | |
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3 dynamics | |
n.力学,动力学,动力,原动力;动态 | |
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4 measles | |
n.麻疹,风疹,包虫病,痧子 | |
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5 density | |
n.密集,密度,浓度 | |
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6 grooming | |
n. 修饰, 美容,(动物)梳理毛发 | |
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7 saliva | |
n.唾液,口水 | |
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8 prey | |
n.被掠食者,牺牲者,掠食;v.捕食,掠夺,折磨 | |
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9 affected | |
adj.不自然的,假装的 | |
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10 vaccinated | |
[医]已接种的,种痘的,接种过疫菌的 | |
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11 intensity | |
n.强烈,剧烈;强度;烈度 | |
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12 vaccination | |
n.接种疫苗,种痘 | |
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13 fatalities | |
n.恶性事故( fatality的名词复数 );死亡;致命性;命运 | |
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14 lethal | |
adj.致死的;毁灭性的 | |
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15 entirely | |
ad.全部地,完整地;完全地,彻底地 | |
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16 vaccines | |
疫苗,痘苗( vaccine的名词复数 ) | |
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17 skunks | |
n.臭鼬( skunk的名词复数 );臭鼬毛皮;卑鄙的人;可恶的人 | |
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