Bovine anaplasmosis and tick-borne pathogens in cattle of the Galapagos Islands

A cross-sectional study was conducted to determine the species of Anaplasma spp. and estimate its prevalence in cattle of the three main cattle-producing Galapagos Islands (Santa Cruz, San Cristóbal and Isabela) using indirect PCR assays, genetic sequencing and ELISA. Ticks were also collected from cattle and scanned for 47 tick-borne pathogens in a 48 × 48 real-time PCR chip. A mixed effects logistic regression was performed to identify potential risk factors explaining Anaplasma infection in cattle. A. phagocytophilum was not detected in any of the tested animals. Genetic sequencing allowed detection of A. platys-like strains in 11 (36.7%) of the 30 Anaplasma spp.-positive samples analysed. A. marginale was widespread in the three islands with a global between-herd prevalence of 100% [89; 100]_{95% CI} and a median within-herd prevalence of 93%. A significant association was found between A. marginale infection and age with higher odds of being positive for adults (OR = 3.3 [1.2; 9.9]_{95% Bootstrap CI} ). All collected ticks were identified as Rhipicephalus microplus. A. marginale, Babesia bigemina, Borrelia theileri and Francisella-like endosymbiont were detected in tick pools. These results show that the Galapagos Islands are endemic for A. marginale.

Estimation of French cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015

BACKGROUND

From 2006 to 2010, France experienced two bluetongue epidemics caused by serotype 1 (BTV-1) and 8 (BTV-8) which were controlled by mass vaccination campaigns. After five years without any detected cases, a sick ram was confirmed in August 2015 to be infected by a BTV-8 strain almost identical to that circulating during the previous outbreak. By then, part of the French cattle population was expected to be still protected, since bluetongue antibodies are known to last for many years after natural infection or vaccination. The objective of this study was to estimate the proportion of cattle in France still immune to BTV-8 at the time of its re-emergence in 2015.

RESULTS

We used BTV group-specific cELISA results from 8525 cattle born before the vaccination ban in 2013 and 15,799 cattle born after the ban. Samples were collected from January to April 2016 to estimate seroprevalence per birth cohort. The overall seroprevalence in cattle at national and local levels was extrapolated from seroprevalence results per birth cohort and their respective proportion at each level. To indirectly assess pre-immune status of birth cohorts, we computed prevalence per birth cohort on infected farms in autumn 2015 using 1377 RT-PCR results. These revealed limited BTV circulation in 2015. Seroprevalence per birth cohort was likely to be connected to past exposure to natural infection and/or vaccination with higher seroprevalence levels in older animals. A seroprevalence of 95% was observed for animals born before 2008, of which > 90% were exposed to two compulsory vaccination campaigns in 2008-2010. None of the animals born before 2008 were found to be infected, unlike 19% of the young cattle which had never been vaccinated. This suggests that most ELISA-positive animals were pre-immune to BTV-8. We estimated that 18% (from 12% to 32% per département) of the French cattle population was probably pre-immune in 2015.

CONCLUSIONS

These results strongly suggest a persistence of antibodies for at least 5-6 years after natural infection or vaccination. The herd immunity of the French cattle population probably limited BTV circulation up to 2015, by which time more than 80% of cattle were naive.

West Nile virus epizootics in the Camargue (France) in 2015 and reinforcement of surveillance and control networks

West Nile virus (WNV) infection is a non-contagious disease mainly transmitted by the bites of infected mosquitoes from the genus Culex. The virus is maintained in a mosquito-bird-mosquito cycle, and can accidentally be transmitted to mammalian hosts. Among mammalian hosts, equines and humans are the most sensitive to WNV infection and can develop severe meningoencephalitis. As WNV infections are zoonotic and can be severe in humans and equines, West Nile fever is considered to be a public and animal health concern. After a silent period of almost ten years, WNV re-emerged in France at the periphery of the Camargue area during the summer of 2015, underlining the fact that the Camargue area creates favourable conditions for WNV emergence and amplification in France. The French Network for Epidemiological Surveillance of Equine Diseases (Réseau d'Épidémio-Surveillance en Pathologie Équine [RESPE]) facilitated the early detection of WNV cases in horses. In total, 49 horses were found to be infected; among them, 44 presented clinical signs, 41 with meningoencephalitis and three with hyperthermia only. Six horses among the 41 with nervous symptoms died from the disease or were euthanised (a case fatality rate of 14.6%). The authors describe the characteristics of the 2015 WNV epizootics, the early detection of the first WNV equine cases via the RESPE network and the coordination of WNV surveillance in France.

Circulation of bluetongue virus 8 in French cattle, before and after the re-emergence in 2015

Bluetongue virus serotype 8 (BTV-8) re-emerged in Central France in August 2015. The viral strain identified is nearly identical to the one that circulated during the 2006/2009 massive outbreak throughout Europe. To address the question of an undetected BTV-8 circulation on the French territory, a serological study was conducted on young cattle along a transect of seven departments, three of them located in areas where the virus presence had been confirmed by RT-PCR by winter 2015/2016. Sera from 2,565 animals were collected during the winters preceding and following the re-emergence, with 414 animals being sampled in each of the two consecutive years. All samples were tested by competitive ELISA (IDVet) and, when enough serum was available, ELISA-positive samples were confirmed by seroneutralization tests. In areas with infected holdings, seropositive animals were found before the re-emergence (N = 14 of 511), significantly more on the following year (N = 17 of 257), and eight animals (N = 158) seroconverted over 2015. Seropositive animals were also detected as early as winter 2014/2015 in one department without known infected holdings (N = 12 of 150), and in winter 2015/2016 in three of them (N = 21 of 555), where seven animals (N = 154) seroconverted over 2015. These results suggest that BTV-8 may have spread at low levels before the re-emergence, even in areas considered virus-free. Unfortunately, whole blood from the seropositive animals was not available to definitely confirm the virus presence by RT-PCR.

Spread rate of lumpy skin disease in the Balkans, 2015-2016

After its introduction in Turkey in November 2013 and subsequent spread in this country, lumpy skin disease (LSD) was first reported in the western Turkey in May 2015. It was observed in cattle in Greece and reported to the World Organization for Animal Health (OIE) in August 2015. From May 2015 to August 2016, 1,092 outbreaks of lumpy skin disease were reported in cattle from western Turkey and eight Balkan countries: Greece, Bulgaria, The Former Yugoslav Republic of Macedonia, Serbia, Kosovo, and Albania. During this period, the median LSD spread rate was 7.3 km/week. The frequency of outbreaks was highly seasonal, with little or no transmission reported during the winter. Also, the skewed distribution of spread rates suggested two distinct underlying epidemiological processes, associating local and distant spread possibly related to vectors and cattle trade movements, respectively.

Parapatric distribution and sexual competition between two tick species, Amblyomma variegatum and A. hebraeum (Acari, Ixodidae), in Mozambique

Background

Amblyomma variegatum and A. hebraeum are two ticks of veterinary and human health importance in south-east Africa. In Zimbabwe they occupy parapatric (marginally overlapping and juxtaposed) distributions. Understanding the mechanisms behind this parapatry is essential for predicting the spatio-temporal dynamics of Amblyomma spp. and the impacts of associated diseases. It has been hypothesized that exclusive competition between these species results from competition at the levels of male signal reception (attraction-aggregation-attachment pheromones) or sexual competition for mates. This hypothesis predicts that the parapatry described in Zimbabwe could also be present in other countries in the region.

Methods

To explore this competitive exclusion hypothesis we conducted field surveys at the two species’ range limits in Mozambique to identify areas of sympatry (overlapping areas) and to study potential interactions (communicative and reproductive interference effects) in those areas. At sympatric sites, hetero-specific mating pairs were collected and inter-specific attractiveness/repellent effects acting at long and short distances were assessed by analyzing species co-occurrences on co-infested herds and co-infested hosts.

Results

Co-occurrences of both species at sampling sites were infrequent and localized in areas where both tick and host densities were low. At sympatric sites, high percentages of individuals of both species shared attachment sites on hosts and inter-specific mating rates were high. Although cross-mating rates were not significantly different for A. variegatum and A. hebraeum females, attraction towards hetero-specific males was greater for A. hebraeum females than for A. variegatum females and we observed small asymmetrical repellent effects between males at attachment sites.

Conclusions

Our observations suggest near-symmetrical reproductive interference between A. variegatum and A. hebraeum, despite between-species differences in the strength of reproductive isolation barriers acting at the aggregation, fixation and partner contact levels. Theoretical models predict that sexual competition coupled with hybrid inviability, greatly reduces the probability of one species becoming established in an otherwise suitable location when the other species is already established. This mechanism can explain why the parapatric boundary in Mozambique has formed within an area of low tick densities and relatively infrequent host-mediated dispersal events.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1116-7) contains supplementary material, which is available to authorized users.

Developing a disease prevention strategy in the Caribbean: the importance of assessing animal health-related risks at regional level

In 2009 CaribVET conducted a survey among Caribbean national Veterinary Services to assess perceptions of risk assessment and to identify the principal exotic diseases of concern in the region and their means of introduction. The results showed that the introduction of live animals was considered the most likely route of introduction of exotic animal pathogens, followed by the uncontrolled introduction of animal products by boat passengers. The results were used to define a regional strategy for assessing animal health risks that highlights the importance of within-region exchanges.