Diagnostic methods used to monitor an outbreak of babesiosis (Babesia bovis) in a herd of feral cattle in New Caledonia.

BACKGROUND: In December 2007, Babesia bovis was introduced to New Caledonia through the importation of cattle vaccinated with a live tick fever (babesiosis and anaplasmosis) vaccine. Medical measures, acaricide and antiprotozoal treatments, and quarantine restrictions were implemented with success on all the farms involved, but the disease spread to one of the neighbouring properties where feral cattle were present. To circumscribe and eliminate this outbreak, the authorities decided to slaughter all animals on the neighbouring property. OBJECTIVES: To monitor the spread of babesiosis in naïve cattle and to compare the usefulness of PCR, ELISA and brain smear for disease detection in monitoring this outbreak. METHODS: Blood and brain samples of slaughtered animals were analysed over time throughout the eradication campaign using serology, PCR and brain smears. In addition, field numbers of Rhipicephalus microplus tick larvae were assessed and Babesia infection of the larvae analysed using PCR. RESULTS: This study showed the natural spread of babesiosis in a naïve herd without pharmacological control measures. Prevalence reached 80% within a year of introduction. ELISA and PCR tests performed similarly in detecting disease in cattle and both were superior to brain smears. Nevertheless, specific tests or combinations of tests may be preferable, depending on the specific requirements of any future disease situation. CONCLUSIONS: In cattle, ELISA and PCR appear to be suitable tools for monitoring the evolution of a babesiosis outbreak, with brain smears as a useful adjunct. PCR was not suitable for detecting infection in tick larvae.

Distribution of Crimean-Congo hemorrhagic fever viral antibody in Senegal: environmental and vectorial correlates.

The spatial pattern in Senegal of Crimean-Congo hemorrhagic fever (CCHF) virus IgG antibody prevalence in human and sheep was determined as was the relative abundance of potential tick vectors. A systematic, country-wide serological survey of sheep demonstrated that 10.4% of sheep exhibited IgG to CCHF virus. Sexes were infected equally. Antibody prevalence increased with age from 2.1% during the first year to 18.2% among sheep greater than or equal to 3 years of age. IgG prevalence was highest in the northern, arid Sahelian zone, averaging 75.7% seropositivity, and decreased to zero in the southern, moister Sudano-Guinean and Guinean zones. Human IgG prevalence ranged from 21% to less than 1% among the 8 sites that were sampled throughout the country, being greatest in the arid north and least in the south. Hyalomma ssp. ticks predominated in those biotopes where antibody prevalence was highest. The abundance of Hyalomma ticks may be the proximal determinant of endemic transmission.

[Prevalence of antibodies against Rift Valley fever virus in sheep and goats in Senegal]. / Prévalence en anticorps contre le virus de la fièvre de la vallée du Rift chez les petits ruminants du Sénégal.

A total of 1,715 randomly selected sheep and goat sera from Senegal were tested for antibodies against Rift Valley fever virus using an enzyme-linked immunosorbent assay. The results showed that Rift Valley fever is enzootic. The prevalence is highly heterogeneous, depending on the area. Sheep and goats expressed comparable antibody prevalence, suggesting that both are involved equally in the virus cycle.

[Epidemiological study of leptospirosis in New Caledonia]. / Etude épidémiologique de la leptospirose en Nouvelle-Calédonie.

This epidemiological survey includes the study of human and animal leptospirosis in New Caledonia from clinical cases as well as a systematic serological study about exposed human and animal populations. The results show that this disease is endemic on the whole territory with a few important focuses in agricultural area, especially on the Western coast. Leptospira icterohemorrhagiae is the main serotype and is responsible for serious human leptospirosis. The male farmers constitute the most exposed population, especially from March to May, end of the host season. In order to reduce the importance of this disease, it is desirable that the farmers are vaccinated and mass media campaigns are necessary to improve the prevention.