Dynamics of natural infection by Anaplasma phagocytophilum in a dairy cattle herd in Brittany, France

First detection of Anaplasma phagocytophilum and Babesia divergens and high infection rates of Anaplasma marginale and Babesia bigemina in cattle in extensive grazing systems of Central Spain

Bovine vector-borne diseases have a considerable economic impact worldwide and affect health of humans and animals. However, different aspects of their epidemiology and their pathogenesis remain unclear. Despite the frequent description of clinical cases reported by practitioners attending cattle from Madrid, Central Spain, molecular prevalence of Anaplasma spp. and Babesia spp. has not been described. The aim of this study was to assess the positivity rate of A. phagocytophilum, A. marginale, A. centrale, B. bigemina and B. divergens in livestock of this area and to evaluate the existence of associations between these pathogens and haematological, biochemical and epidemiological data. Babesia divergens and A. phagocytophilum were detected for the first time in cattle from Madrid. Their positivity percentages were low (2.2% ± 1.4% and 1.8% ± 1.2%, respectively), but this description is of special interest, as these agents are potentially zoonotic. Both agents were found in areas of higher altitude and relative humidity and lower temperature. The detection of ticks in livestock during the moment of sampling was confirmed as a risk factor for these infections. Anaplasma marginale showed the highest molecular infection rate (30% ± 4.1%) in this study, followed by B. bigemina (21.9% ± 3.7%). Higher positivity rates of A. marginale and B. bigemina were found in the areas of mountain climate and warm-summer continental Mediterranean climate. The use of ectoparasiticide treatment was found as a risk factor for infection by A. marginale and B. bigemina. This finding could lead to reconsider the ectoparasiticide protocols that are used nowadays. Grazing on pastures with domestic or wild ruminants and the presence of wild carnivores were associated with higher rates of infection by these four agents and coinfections were frequently found.

Severe Anaplasma phagocytophilum and Babesia divergens Concomitant Infection in Imported Captive Reindeer (Rangifer tarandus)

Tick-borne diseases are highly prevalent in domestic and wild ruminants and they may be distributed in wide geographical ranges by animal transportation. The aim of the current study was to investigate the presence of European strains of Babesia spp. and/or Anaplasma spp. in oversea imported reindeer specimens. Imported specimens (n=7) were hospitalized with visible tick infestation (Ixodes ricinus) and signs of cachexia, anemia, and hemoglobinuria. Using blood smears, PCR, and BLAST comparisons, it was confirmed that the animals were infected with a French strain of Anaplasma phagocytophilum and Babesia divergens which is considered to be absent in the USA. We conclude that oversea importation of reindeers must be followed with a routine check for geographically-specific strains of pathogens from the place of origin. This monitoring process must be dynamic and according to recent reports of tick-borne pathogens.

Epidemiology, genetic variants and clinical course of natural infections with Anaplasma phagocytophilum in a dairy cattle herd

Background

Anaplasma phagocytophilum is an obligate intracellular, tick-transmitted bacterium that causes granulocytic anaplasmosis in humans and several mammalian species including domestic ruminants where it is called tick-borne fever (TBF). Different genetic variants exist but their impact with regard to putative differences in host associations and pathogenicity are not yet completely understood.

Methods

Natural infections with A. phagocytophilum in a dairy cattle herd in Germany were investigated over one pasture season by using serology, haematology, blood chemistry and polymerase chain reaction (PCR). Sequence analysis of partial 16S rRNA, groEL, msp2 and msp4 genes of A. phagocytophilum was carried out in order to trace possible genetic variants and their relations between cattle, roe deer (Capreolus capreolus) and ticks (Ixodes ricinus) in this area.

Results

In total 533 samples from 58 cattle, 310 ticks, three roe deer and one wild boar were examined. Our results show (i) typical clinical symptoms of TBF in first-time infected heifers, such as high fever, reduced milk yield, lower limb oedema and typical haematological and biochemical findings such as severe leukopenia, erythropenia, neutropenia, lymphocytopenia, monocytopenia, a significant increase in creatinine and bilirubin and a significant decrease in serum albumin, γ-GT, GLDH, magnesium and calcium; (ii) a high overall prevalence of A. phagocytophilum infections in this herd as 78.9% (15/19) of the naïve heifers were real-time PCR-positive and 75.9% (44/58) of the entire herd seroconverted; and (iii) a high level of sequence variation in the analysed genes with five variants of the 16S rRNA gene, two variants of the groEL gene, three variants of the msp2 gene and four variants in the msp4 gene with certain combinations of these variants.

Conclusions

In cattle particular combinations of the genetic variants of A. phagocytophilum occurred, whereas three roe deer showed different variants altogether. This is indicative for a sympatric circulation of variants in this small geographical region (< 1 km²). Both re- and superinfections with A. phagocytophilum were observed in five cattle showing that infection does not result in sterile immunity. For prevention of clinical cases we suggest pasturing of young, not pregnant heifers to reduce economical losses.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2570-1) contains supplementary material, which is available to authorized users.

Host specificity, pathogen exposure, and superinfections impact the distribution of Anaplasma phagocytophilum genotypes in ticks, roe deer, and livestock in a fragmented agricultural landscape

Anaplasma phagocytophilum is a bacterial pathogen mainly transmitted by Ixodes ricinus ticks in Europe. It infects wild mammals, livestock, and, occasionally, humans. Roe deer are considered to be the major reservoir, but the genotypes they carry differ from those that are found in livestock and humans. Here, we investigated whether roe deer were the main source of the A. phagocytophilum genotypes circulating in questing I. ricinus nymphs in a fragmented agricultural landscape in France. First, we assessed pathogen prevalence in 1837 I. ricinus nymphs (sampled along georeferenced transects) and 79 roe deer. Prevalence was dramatically different between ticks and roe deer: 1.9% versus 76%, respectively. Second, using high-throughput amplicon sequencing, we characterized the diversity of the A. phagocytophilum genotypes found in 22 infected ticks and 60 infected roe deer; the aim was to determine the frequency of co-infections. Only 22.7% of infected ticks carried genotypes associated with roe deer. This finding fits with others suggesting that cattle density is the major factor explaining infected tick density. To explore epidemiological scenarios capable of explaining these patterns, we constructed compartmental models that focused on how A. phagocytophilum exposure and infection dynamics affected pathogen prevalence in roe deer. At the exposure levels predicted by the results of this study and the literature, the high prevalence in roe deer was only seen in the model in which superinfections could occur during all infection phases and when the probability of infection post exposure was above 0.43. We then interpreted these results from the perspective of livestock and human health.

First molecular survey and novel genetic variants' identification of Anaplasma marginale, A. centrale and A. bovis in cattle from Tunisia

Few data are available about the presence and distribution of Anaplasma species in cattle in North African countries. In this study prevalence, co-infections, risk factors and genetic diversity of Anaplasma species were evaluated in bovines from Northern Tunisia. A total of 232 cattle from 36 randomly selected farms in three Tunisian localities were investigated for the presence of Anaplasma species in blood by Real-time PCR and/or nested PCR. Overall infection rates of Anaplasma spp., Anaplasma marginale, Anaplasma centrale and Anaplasma bovis were 34.9%, 25.4%, 15.1%, and 3.9%, respectively. Anaplasma phagocytophilum was not detected in cattle. The most common co-infection pattern was an association of A. marginale and A. centrale (11.2%). Five cattle (2.1%) all reared in the sub-humid bioclimatic area, were co-infected by the three Anaplasma species. Molecular prevalence of Anaplasma infection varied significantly according to locality, bioclimatic area, tick infestation and type of breeding. Animals of the Holstein breed were less infected by A. marginale and A. centrale than other breeds. Genetic analysis of A. marginale msp4 gene indicated a high sequence diversity of Tunisian strains, suggesting a multiple introduction of infected cattle from different origins. Phylogenetic studies based on the 16S rRNA gene showed that the most prevalent A. centrale strains were closely related to the A. centrale vaccine strain. Moreover, all A. bovis variants clustered with other A. bovis sequences obtained from domestic and wild ruminant strains. This is the first molecular investigation on Anaplasma species in Tunisian cattle providing pivotal background for designing epidemiological studies and to develop control strategies in the country.

High Prevalence of Anaplasma spp. in Small Ruminants in Morocco

The prevalence of infection by Anaplasma spp. (including Anaplasma phagocytophilum) was determined using blood smear microscopy and PCR through screening of small ruminant blood samples collected from seven regions of Morocco. Co-infections of Anaplasma spp., Babesia spp, Theileria spp. and Mycoplasma spp. were investigated and risk factors for Anaplasma spp. infection assessed. A total of 422 small ruminant blood samples were randomly collected from 70 flocks. Individual animal (breed, age, tick burden and previous treatment) and flock data (GPS coordinate of farm, size of flock and livestock production system) were collected. Upon examination of blood smears, 375 blood samples (88.9%) were found to contain Anaplasma-like erythrocytic inclusion bodies. Upon screening with a large spectrum PCR targeting the Anaplasma 16S rRNA region, 303 (71%) samples were found to be positive. All 303 samples screened with the A. phagocytophilum-specific PCR, which targets the msp2 region, were found to be negative. Differences in prevalence were found to be statistically significant with regard to region, altitude, flock size, livestock production system, grazing system, presence of clinical cases and application of tick and tick-borne diseases prophylactic measures. Kappa analysis revealed a poor concordance between microscopy and PCR (k = 0.14). Agreement with PCR is improved by considering microscopy and packed cell volume (PCV) in parallel. The prevalence of double infections was found to be 1.7, 2.5 and 24% for Anaplasma-Babesia, Anaplasma-Mycoplasma and Anaplasma-Theileria, respectively. Co-infection with three or more haemoparasites was found in 1.6% of animals examined. In conclusion, we demonstrate the high burden of anaplasmosis in small ruminants in Morocco and the high prevalence of co-infections of tick-borne diseases. There is an urgent need to improve the control of this neglected group of diseases.

Anaplasma phagocytophilum--a widespread multi-host pathogen with highly adaptive strategies

The bacterium Anaplasma phagocytophilum has for decades been known to cause the disease tick-borne fever (TBF) in domestic ruminants in Ixodes ricinus-infested areas in northern Europe. In recent years, the bacterium has been found associated with Ixodes-tick species more or less worldwide on the northern hemisphere. A. phagocytophilum has a broad host range and may cause severe disease in several mammalian species, including humans. However, the clinical symptoms vary from subclinical to fatal conditions, and considerable underreporting of clinical incidents is suspected in both human and veterinary medicine. Several variants of A. phagocytophilum have been genetically characterized. Identification and stratification into phylogenetic subfamilies has been based on cell culturing, experimental infections, PCR, and sequencing techniques. However, few genome sequences have been completed so far, thus observations on biological, ecological, and pathological differences between genotypes of the bacterium, have yet to be elucidated by molecular and experimental infection studies. The natural transmission cycles of various A. phagocytophilum variants, the involvement of their respective hosts and vectors involved, in particular the zoonotic potential, have to be unraveled. A. phagocytophilum is able to persist between seasons of tick activity in several mammalian species and movement of hosts and infected ticks on migrating animals or birds may spread the bacterium. In the present review, we focus on the ecology and epidemiology of A. phagocytophilum, especially the role of wildlife in contribution to the spread and sustainability of the infection in domestic livestock and humans.