Surveillance of avian influenza in the Caribbean through the Caribbean Animal Health Network: surveillance tools and epidemiologic studies.

The Caribbean region is considered to be at risk for avian influenza (AI) due to a large backyard poultry system, an important commercial poultry production system, the presence of migratory birds, and disparities in the surveillance systems. The Caribbean Animal Health Network (CaribVET) has developed tools to implement AI surveillance in the region with the goals to have 1) a regionally harmonized surveillance protocol and specific web pages for AI surveillance on www.caribvet.net, and 2) an active and passive surveillance for AI in domestic and wild birds. A diagnostic network for the Caribbean, including technology transfer and AI virus molecular diagnostic capability in Guadeloupe (real-time reverse transcription-polymerase chain reaction for the AI virus matrix gene), was developed. Between 2006 and 2009, 627 samples from four Caribbean countries were tested for three circumstances: importation purposes, following a clinical suspicion of AI, or through an active survey of wild birds (mainly waders) during the southward and northward migration periods in Guadeloupe. None of the samples tested were positive, suggesting a limited role of these species in the AI virus ecology in the Caribbean. Following low pathogenic H5N2 outbreaks in the Dominican Republic in 2007, a questionnaire was developed to collect data for a risk analysis of AI spread in the region through fighting cocks. The infection pathway of the Martinique commercial poultry sector by AI, through introduction of infected cocks, was designed, and recommendations were provided to the Caribbean Veterinary Services to improve cock movement control and biosecurity measures. The CaribVET and its organization allowed interaction between diagnostic and surveillance tools on the one hand and epidemiologic studies on the other, both of them developed in congruence with regional strategies. Together, these CaribVET activities contribute to strengthening surveillance of avian influenza virus (AIV) in the Caribbean region and may allow the development of research studies on both AI risk analysis and on AIV ecology.

Cattle nematodes resistant to macrocyclic lactones: comparative effects of P-glycoprotein modulation on the efficacy and disposition kinetics of ivermectin and moxidectin.

The role of the drug efflux pump, known as P-glycoprotein, in the pharmacokinetic disposition (host) and resistance mechanisms (target parasites) of the macrocyclic lactone (ML) antiparasitic compounds has been demonstrated. To achieve a deeper comprehension on the relationship between their pharmacokinetic and pharmacodynamic behaviors, the aim of the current work was to assess the comparative effect of loperamide, a well-established P-glycoprotein modulator, on the ivermectin and moxidectin disposition kinetics and efficacy against resistant nematodes in cattle. Fifty (50) Aberdeen Angus male calves were divided into five (5) experimental groups. Group A remained as an untreated control. Animals in the other experimental Groups received ivermectin (Group B) and moxidectin (Group C) (200 microg/kg, subcutaneously) given alone or co-administered with loperamide (0.4 mg/kg, three times every 24 h) (Groups D and E). Blood samples were collected over 30 days post-treatment and drug plasma concentrations were measured by HPLC with fluorescence detection. Estimation of the anthelmintic efficacy for the different drug treatments was performed by the faecal egg count reduction test (FECRT). Nematode larvae were identified by pooled faecal cultures for each experimental group. Cooperia spp. and Ostertagia spp. were the largely predominant nematode larvae in pre-treatment cultures. A low nematodicidal efficacy (measured by the FECRT) was observed for both ivermectin (23%) and moxidectin (69%) in cattle, which agrees with a high degree of resistance to both molecules. Cooperia spp. was the most abundant nematode species recovered after the different drug treatments. The egg output reduction values increased from 23% to 50% (ivermectin) and from 69% to 87% (moxidectin) following their co-administration with loperamide. Enhanced systemic concentrations and an altered disposition of both ML in cattle, which correlates with a tendency to increased anthelmintic efficacy, were observed in the presence of loperamide. Overall, the in vivo modulation of P-glycoprotein activity modified the kinetic behavior and improved the efficacy of the ML against resistant nematodes in cattle. The work provides further evidence on the high degree of resistance to ML in cattle nematodes and, shows for the first time under field conditions, that modulation of P-glycoprotein may be a valid pharmacological approach to improve the activity and extend the lifespan of these antiparasitic molecules.

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.