A campaign to eradicate bovine babesiosis from New Caledonia

Abstract

In December 2007, Babesia bovis was introduced to New Caledonia through the importation of cattle that had been vaccinated with a live tick fever (babesiosis and anaplasmosis) vaccine. Although the tick Rhipicephalus (Boophilus) microplus is common in New Caledonia, the territory had previously been free of tick-borne diseases of cattle. This paper describes the initial extent of the outbreak, the measures and rationale for disease control, and the progress to date of the eradication campaign. Initially, 22 properties were affected involving approximately 2300 cattle in 'high risk' zones and 1600 in adjoining 'suspect' zones. Rather than slaughtering infected herds or attempting to eliminate the tick vector, the campaign was based on quarantine of affected properties, and aggressive tick control in conjunction with 3-monthly treatments of the high risk cattle with the antiprotozoal drug imidocarb dipropionate. Subsequent surveillance by ELISA and PCR showed a progressive and dramatic decline in seroprevalence among infected herds and the absence of new infections. All 22 properties were considered to be free of Babesia within 12 months of the start of the disease control program. These results indicate that the strategy was effective in eliminating Babesia from infected herds and feasible as an eradication strategy on a moderately large scale. Unfortunately, early in the campaign, babesiosis spread to a herd of feral cattle on a property in the 'suspect' zone, and this reservoir of infection subsequently resulted in the infection (or reinfection) of cattle on several neighbouring commercial farms. The eradication campaign in New Caledonia is currently focussed on destocking the feral cattle - extensive surveillance suggests that this is the only remaining nidus of infection.