Analysis of Amblyomma surveillance data in the Caribbean: lessons for future control programmes.

Amblyomma variegatum, the Tropical Bont Tick (TBT), is the principal vector of heartwater and is associated with dermatophilosis, major causes of losses in animal production and mortality in Caribbean livestock. From 1995 to 2007, the Caribbean Amblyomma Programme (CAP) supported treatment and surveillance activities in 11 islands of the Eastern Caribbean with an initial objective of eradicating TBT. In addition to control activities, surveillance data were collected between 1997 and 2006 in a unique regional database. We report the analysis of the surveillance data from four islands (Nevis, St Kitts, St Lucia, and Barbados) where control and surveillance followed the initial protocol and where enough data were collected. We describe the evolution of TBT infestation levels and the efforts carried out throughout the surveillance period. Logistic regression identified factors associated with herds found infested with TBT. Overall, treatment programmes were associated with a decrease in proportion of TBT-infested farms. High surveillance efforts were carried out throughout the 1997-2007 period for all island of interest, but inadequate level of surveillance was observed in several quarters especially for St Kitts. Third quarter of the year, as indication of adult TBT seasonality on livestock, was significantly associated with the risk of detecting TBT in Nevis and St Kitts livestock farms. Also, presence of cattle in Nevis farms was shown associated with an increasing probability of farms being declared TBT-infested. Outcomes of these analyses provide basis for recommendations to improve future national and regional control and surveillance activities. This analysis demonstrates the usefulness of long term and adequate surveillance data for control programmes and identification of factors associated with risk of having infested herds.