Rahajarison P.,FOFIFA DRZV |
Arimanana A.H.,FOFIFA DRZV |
Raliniaina M.,FOFIFA DRZV |
Stachurski F.,FOFIFA DRZV |
And 2 more authors.
Infection, Genetics and Evolution | Year: 2014
Although Amblyomma variegatum is now regularly recorded up to 1600. m in altitude in the Malagasy highlands, where it was previously reported not to persist without a constant supply of ticks introduced from lower infested regions, some parts of the highlands remain tick-free. Studies were carried out to verify whether the cold climate prevailing in these areas in June-September could prevent the survival and moulting of nymphs, the tick life stage present in the environment at this period. Cohorts of engorged A. variegatum nymphs were released from June to August in six different sites (three in 2010, altitudes 1200-1415. m; three in 2011, altitudes 1585-1960. m) which were reported to be either tick-infested (two in 2010, one in 2011) or tick-free. The ticks were placed in cages driven into the soil and open at the bottom so that they could hide in the soil or root network. Of the 1975 nymphs released in 2010 and the 1494 released in 2011, 86% and 85% were recovered, respectively. Twenty to 23% of the recovered ticks were dead, and some of them were obviously predated; predation also likely contributed to the disappearance of the non-recovered ticks. When the rainy season started in October, 59% of the newly moulted adults were still alive in the cages. The moulting period lasted up to 20. weeks, depending on the site and release period. As verified in 2011, unfed nymphs could also survive the cold season. Various A. variegatum life stages are thus able to survive the adverse cold and/or dry seasons: unfed nymphs, engorged nymphs in developmental diapause, moulted adults in behavioural diapause as observed previously. Strong variation in mortality and recovery rates was observed between cages, highlighting the importance of the micro-environment and micro-climate for tick survival. The minimum temperature recorded in the field sites varied from 1.1. °C to 6.8. °C, but the tick-free sites were not the coldest ones; they were, however, those for which the temperature remained below 10. °C for the longest time over the study period. Recovery and mortality rates in the tick-free sites were similar to those of the tick-infested sites: the temperatures recorded during the study periods did not prevent ticks from surviving and moulting although it did delay the metamorphosis. Low temperature alone can therefore not explain the persistence of tick-free areas in the highlands. To further monitor survival, cohorts of engorged nymphs were also maintained in an incubator at 3.6. °C, 6.2. °C or 12.8. °C. More than 50% mortality was observed after 6. days at 3.6. °C, and after 15. days at 6.2. °C, whereas 18. days at 12.8. °C only delayed moulting. The collected survival, moulting and climatic data presented in this study should help to develop a predictive model to assess the distribution of A. variegatum according to climate characteristics. © 2014 Elsevier B.V.
Nicolas G.,CIRAD - Agricultural Research for Development |
Nicolas G.,French Agency for Food Environmental and Occupational Health and Safety |
Durand B.,French Agency for Food Environmental and Occupational Health and Safety |
Duboz R.,CIRAD - Agricultural Research for Development |
And 3 more authors.
Acta Tropica | Year: 2013
In 2008-2009 a Rift Valley Fever (RVF) outbreak occurred in the Anjozorobe area, a temperate and mountainous area of the Madagascar highlands. The results of a serosurvey conducted in 2009 suggested recurrent circulation of RVF virus (RVFV) in this area and potential involvement of the cattle trade in RVFV circulation. The objective of this study was to describe the cattle trade network of the area and analyse the link between network structure and RVFV circulation. Five hundred and sixteen animals that tested negative in 2009 were sampled again in 2010. The 2009-2010 cattle-level seroconversion rate was estimated at 7% (95% CI: 5-10%). Trade data from 386 breeders of 48 villages were collected and analysed using social network analysis methodology, nodes being villages and ties being any movements of cattle connecting villages. The specific practice of cattle barter, known as kapsile, that involves frequent contacts between cattle of two breeders, was observed in addition to usual trade. Trade data were analysed using a logistic model, the occurrence of seroconversion at the village level being the outcome variable and the network centrality measures being the predictors. A negative association was observed between the occurrence of seroconversion in the village and introduction of cattle by trade (p=0.03), as well as the distance to the nearest water point (p=0.002). Conversely, the practice of kapsile, was a seroconversion risk factor (p=0.007). The kapsile practice may be the support for inter-village RVFV circulation whereas the trade network is probably rather implicated in the introduction of RVFV to the area from other parts of Madagascar. The negative association of the distance to the nearest water point suggests that after RVFV introduction, a substantial part of transmission may be due to vectors. © 2013 Elsevier B.V.
Cappelle J.,CIRAD - Agricultural Research for Development |
Cappelle J.,Institute Pasteur in Cambodia |
Caron A.,CIRAD - Agricultural Research for Development |
Caron A.,University of Pretoria |
And 17 more authors.
Epidemiology and Infection | Year: 2015
Newcastle disease (ND) is one of the most important poultry diseases worldwide and can lead to annual losses of up to 80% of backyard chickens in Africa. All bird species are considered susceptible to ND virus (NDV) infection but little is known about the role that wild birds play in the epidemiology of the virus. We present a long-term monitoring of 9000 wild birds in four African countries. Overall, 3.06% of the birds were PCR-positive for NDV infection, with prevalence ranging from 0% to 10% depending on the season, the site and the species considered. Our study shows that ND is circulating continuously and homogeneously in a large range of wild bird species. Several genotypes of NDV circulate concurrently in different species and are phylogenetically closely related to strains circulating in local domestic poultry, suggesting that wild birds may play several roles in the epidemiology of different NDV strains in Africa. We recommend that any strategic plan aiming at controlling ND in Africa should take into account the potential role of the local wild bird community in the transmission of the disease. © Cambridge University Press 2014.
Porphyre V.,CIRAD |
Rasamoelina-Andriamanivo H.,FOFIFA DRZV |
Rasamoelina-Andriamanivo H.,University of Antananarivo |
Rakotoarimanana A.,University of Antananarivo |
And 4 more authors.
Parasites and Vectors | Year: 2015
Background: Taenia solium cysticercosis is a parasitic meat-borne disease that is highly prevalent in pigs and humans in Africa, but the burden is vastly underestimated due to the lack of official control along the pork commodity chain, which hampers long-term control policies. Methods: The apparent and corrected prevalences of T. solium cysticercosis were investigated in pork carcasses slaughtered and retailed in Antananarivo (Madagascar), thanks to a 12-month monitoring plan in two urban abattoirs. Results: Overall apparent prevalence was estimated at 4.6 % [4.2-5.0 %]. The corrected overall prevalence defined as the estimated prevalence after accounting for the sensitivity of meat inspection was 21.03 % [19.18-22.87 %]. Significant differences among geoclimatic regions were observed only for indigenous pigs, with an apparent prevalence estimated at 7.9 % [6.0-9.9 %] in the northern and western regions, 7.3 % [6.0-8.6 %] in the central region, and 6.2 % [4.7-7.8 %] in the southern region. In the central region, where both exotic and indigenous pigs were surveyed, indigenous pigs were 8.5 times [6.7-10.7] more likely to be infected than exotic improved pigs. Urban consumers were more likely to encounter cysticercosis in pork in the rainy season, which is a major at risk period, in particular in December. Differences between abattoirs were also identified. Conclusion: Our results underline the need for improved surveillance and control programmes to limit T. solium cysticercosis in carcasses by introducing a risk-based meat inspection procedure that accounts for the origin and breed of the pigs, and the season. © 2015 Porphyre et al.
Guerrini L.,CIRAD RP PCP |
Guerrini L.,Charles Sadron Institute |
Paul M.C.,National Polytechnic Institute of Toulouse |
Leger L.,Charles Sadron Institute |
And 6 more authors.
Geospatial Health | Year: 2014
While the spatial pattern of the highly pathogenic avian influenza H5N1 virus has been studied throughout Southeast Asia, little is known on the spatial risk factors for avian influenza in Africa. In the present paper, we combined serological data from poultry and remotely sensed environmental factors in the Lake Alaotra region of Madagascar to explore for any association between avian influenza and landscape variables. Serological data from cross-sectional surveys carried out on poultry in 2008 and 2009 were examined together with a Landsat 7 satellite image analysed using supervised classification. The dominant landscape features in a 1-km buffer around farmhouses and distance to the closest water body were extracted. A total of 1,038 individual bird blood samples emanating from 241 flocks were analysed, and the association between avian influenza seroprevalence and these landcape variables was quantified using logistic regression models. No evidence of the presence of H5 or H7 avian influenza subtypes was found, suggesting that only low pathogenic avian influenza (LPAI) circulated. Three predominant land cover classes were identified around the poultry farms: Grassland savannah, rice paddy fields and wetlands. A significant negative relationship was found between LPAI seroprevalence and distance to the closest body of water. We also found that LPAI seroprevalence was higher in farms characterised by predominant wetlands or rice landscapes than in those surrounded by dry savannah. Results from this study suggest that if highly pathogenic avian influenza H5N1 virus were introduced in Madagascar, the environmental conditions that prevail in Lake Alaotra region may allow the virus to spread and persist.