Angela Morrow
Bio 1615
Professor Jama
Transmission Dynamics and Prospects for the Elimination of Canine Rabies
Rabies is a virus that causes inflammation of the brain. It is spread through dog’s saliva
when they bite. The neurological phase of the development of the virus often results in increased
aggression of the host which usually causes them to bite. Once infected it is usually a death
sentence for the host because it progresses very quickly. After symptoms appear people will
most likely die within four or five days unless they are given treatment for the disease.
Every year thousands of people die in third world countries from the canine rabies virus.
Through extensive vaccination programs, the rabies virus has almost been completely eliminated
from the population in North America and Western Europe. The scientists who conducted this
study wanted to find out if it would be possible to eliminate the rabies virus worldwide using the
rabies vaccine.
The study was done in two parts of Tanzania, Serengeti and Ngorongoro. Both areas have
a horrible outbreak of rabies because of the large stray dog populations. Serengeti has a very
large dog population, 9.38 dogs per square km, and Ngorongoro has a much smaller dog
population, 1.36 dogs per square km. The study took 5 years to complete. During that time they
spent countless hours gathering information. Visits were made to areas where there was a
suspected rabid dog, incidents were mapped on site, and villages were interviewed about the
animals, and its possible source of exposure and who it may have bitten. They also interviewed
local veterinarians, livestock officers and community officials. Brain samples were taken from
suspected animals (after they died) but improper storage of the samples led sample deterioration.
However, a large number of samples taken from suspected cases of rabies tested positive for the
disease, approximately 75%. If they received multiple reports within the same homestead area on
multiple or consecutive days of a rabid animal they assumed that it was the same animal and
counted all reports as one.
During the five year study period they had multiple vaccine campaigns. They found that
when the number of animals vaccinated exceeded 70% of the total animal population there were
almost no outbreaks of rabies. When villages had lower than 70% coverage there were more
outbreaks and the largest number of outbreaks occurred when less than 20% of the animal
population was vaccinated. More than 300 vaccinated dogs were reported to have been bitten by
an infected animal and only 10 of those dogs became infected.
Their findings conclude that elimination worldwide of the canine rabies virus is possible
if 60% of the animals that are at risk to the virus are vaccinated against it. The study found that
when a level of 60% of the population is maintained as being vaccinated against the disease then
the incidences of rabies declined despite high occurrences of the disease in neighboring areas.
They also found that vaccinations given to local dog populations could transform into savings for
the public health. They believe that there needs to be a continuous commitment to maintaining
vaccination coverage in domestic dog populations worldwide in order to get rid of the virus.
Hampson K, Dushoff J, Cleaveland S, Haydon DT, Kaare M, et al. (2009) Transmission
Dynamics and Prospects for the Elimination of Canine Rabies. PLoS Biol 7(3): e1000053.
doi:10.1371/journal.pbio.1000053