At present, heartwater in the Caribbean is known with certainty only on Guadeloupe, Marie Galante and Antigua; the first 2 islands are widely infected.
The most important factors responsible for particular aspects of heartwater in Guadeloupe are:
• Cowdria ruminantium of high virulence.
• A very resistant cattle population (Creole), not normally clinically affected.
• A fairly susceptible goat population (Creole) (22% goats born in endemic areas die after experimental inoculation) which, fortunately, includes breeding lines with inherited resistance characteristics.
• Amblyomma variegatum which is present all over the island and all through the year, but with a low infection rate (1-2 % of adult ticks are infected) because of the short period of rickettsemia in infected animals. The low rate of tick infection results in a low endemicity of the disease.
For goats, the epidemiologic situation can be regarded as unstable because the low rate of infection in ticks does not allow a natural immunization of the majority of young kids when they still have a non-specific resistance.
The possible evolution of heartwater in the Caribbean and in the United States is considered.
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