Epidemiology (cont.):
Susceptibility to bovine babesiosis is dependent on a number of factors and outbreaks of the disease are usually related to one of the following: |
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| Outbreaks of bovine babesiosis occur when animals are
transported from a "free zone" into an endemic area or an area of enzootic
instability. They are completely susceptible to the disease.
The cattle in the photo on the right were shipped to Rio Grande do Sul, Brazil, an area of enzootic instability, from a babesia-free area in Uruguay. |
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Young animals are naturally resistant to babesiosis due
to passive immunity. Then, as ticks feed on them, they are continually boosted,
creating immunity to the disease. However, if there is a cold period and lack of infecting ticks, when the ticks return with the warmer weather, animals' immunity has waned and there is susceptibility. |
| The heat-resistant Asian breeds experience less severe disease and have a lower mortality rate than the European breeds. |  |
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Consequently, as higher-producing Holsteins or Jerseys are introduced into the tropics, disease emergence may be seen. |
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The number of ticks feeding on an animal at any one time is a factor. If there is a very high inoculum of Babesia, pre-existing resistance factors may be overwhlemed. |
| Control of babesiosis is often exercised through the use of rigid acaricide treatments. Animals are driven through a "tick dip", containing chemicals that will kill all attached ectoparasites. Lack of conformity to a regular schedule can result in outbreaks of babesiosis. |  |
| When the animals are treated for babesisosis they may recover although very slowly. It was calculated that tick diseases in Brazil mean direct and indirect losses of about a billion dollars per year, based upon cost of control, loss of production, and mortality of livestock. Data from Mexico suggest that the situation in Mexico is similar to Brazil. |