One dead Saskatchewan prairie dog struck fear into the hearts of, well, very few people recently, as Canadian headlines shouted "Plague". What killed this prairie dog?
A Death in the Park
In July 2010, researchers found a dead prairie dog in Grasslands National Park in Saskatchewan, Canada. It was tested and found to have succumbed to sylvatic plague.
This plague is caused by the same bacterium, Yersinia pestis, that also manifests as bubonic plague and pneumonic plague. It was known as the Black Death when it devastated Europe during the Middle Ages.
The way people become infected by the plague is to be bitten by an infected flea. In Europe, rats are blamed as the carriers of the Black Death, since fleas would bite both humans and animals.
Scientists had been puzzled by the spread of plague in the prairie dog population. These animals live in large colonies, called towns; but they socialize with only a few relatives in smaller groups known as coteries. Since there is little interaction across the coteries, outbreaks of disease should be confined to a few families.
Yet the prairie dog population has dropped significantly over several decades - more than could be explained by loss of habitat or hostile farmers. Sometime after a town's population dies out, new families move in. By then the plague should be eliminated, as the fleas would not still be there. Yet the plague will re-emerge.
The Stanford University study determined that the fleas are also "leeching" on grasshopper mice. These are carnivorous mice that eat grasshoppers (and other insects), small rodents or other mammals. The grasshopper mouse seems to be immune to the plague, but is a silent carrier of the bacterium. These mice co-habit with the prairie dogs, but freely cross coterie boundaries.
So the plague can easily kill a few families of prairie dogs because they share their fleas. Since the families are isolated, and the fleas do not travel far by themselves, that should be the end of the outbreak. But if there are enough grasshopper mice in the colony, they will provide transportation for the infected fleas to find new prairie dogs to bite - and infect with plague.
The Implications are Not Too Grim
There is nothing very novel about plague infesting prairie dog towns. These animals are widespread in western North America, and have been subject to this disease since the late 1800s. The scientific breakthrough is finding that grasshopper mice are part of the disease cycle.
Scientists say that the risk to a person is "very low", and it is "very rare" for a person to contract the disease. The last Canadian case of plague occurred in 1939; the last death in 1924. Americans do have annual reports of plague, but fewer than two dozen per year.
Grasslands National Park officials offer very standard advice to visitors, who are still permitted into the park:
- Do not walk through prairie dog towns
- Do not handle dead animals
- Do not let pets roam through these areas (since cats and dogs may also catch the plague from flea bites)
- Wear shoes rather than sandals, high socks, and long pants to reduce the chance of fleas latching on
- Spray insect repellent on shoes, socks and pant legs when in the park
Grasslands National Park is about 350 kilometres (217 miles) south-west of Regina. It borders on Montana and is about 240 Km (150 miles) north-north-west of Glasgow. (Distances are along recommended driving routes; crows would fly by shorter routes).
The death of this one prairie dog is a grim reminder that plague stalks even these small mammals.
References:
Globe and Mail, " Dead Saskatchewan prairie dog found with the plague ", published Aug. 13, 2010, referenced Aug. 14, 2010.
Saskatchewan Health, " Naturally Occuring Plague in Prairie Dogs ", referenced Aug. 14, 2010.
Sarah Richter, Global Regina, " Bubonic plague discovered in one of Sask's national parks ", published Aug. 3 2010, referenced Aug. 14, 2010.
Science Daily report from Stanford University, "Carnivorous Mice Spread Deadly Plague in Prairie Dog Towns, Study Finds", published Aug. 3 2010, referenced Aug. 14, 2010.
Bill Willis, Worsley School, "Carnivorous Mice", 2001, published Aug. 3 2010, referenced Aug. 14, 2010.
Mike DeHaan - Copyright (c) Mike DeHaan, B. Math., of DeHaan Services. Well written and well researched freelance articles; ghost writing for clients.
Join the Conversation