Epidemiology and evolution of the genetic variability of Anaplasma marginale in South Africa

Molecular surveillance and genetic diversity of Anaplasma spp. in cattle (Bos taurus) and goat (Capra aegagrus hircus) from Hainan island/province, China

Anaplasmosis is a highly prevalent tick-borne intracellular bacterial disease that affects various host species globally, particularly ruminants in tropical and subtropical regions. However, information regarding the distribution and epidemiology of anaplasmosis in small and large ruminants on Hainan Isalnd is limited. To address this knowledge gap, the present study aimed to assess the occurrence of Anaplasma spp. infections in goats (N = 731) and cattle (N = 176) blood samples using nested PCR and conventional PCR based assays. The results revealed an overall prevalence of 30.1% in goats and 14.8% in cattle. The infection rates of A. bovis, A. phagocytophilum, A. ovis and A. capra in goat samples were 22.7%, 13.8%, 2.0% and 3.4%, respectively, while the infection rates of A. bovis, A. phagocytophilum and A. marginale in cattle samples were 11.4%, 6.3% and 5.7%, respectively. A. bovis exhibited the highest prevalence among the Anaplasma spp. in both goat and cattle samples. In addition, the most frequent co-infection was the one with A. phagocytophilum and A. bovis. It was found that the age, sex and feeding habits of cattle and goats were considered to be important risk factors. Evaluation of the risk factor relating to the rearing system showed that the infection rate for the free-range goats and cattle was significantly higher when compared with stall-feeding system.This study represents one of the largest investigations on the distribution, prevalence, and risk factors associated with Anaplasma infection in ruminants on Hainan Island, highlighting a higher circulation of the infection in the region than previously anticipated. Further reasesrch is necessary to investigate tick vectors, reservoir animals, and the zoonotic potential of the Anaplasma spp. in this endemic region of Hainan Island.

Anaplasma Species in Africa-A Century of Discovery: A Review on Molecular Epidemiology, Genetic Diversity, and Control

Anaplasma species, belonging to the family Anaplasmataceae in the order Rickettsiales, are obligate intracellular bacteria responsible for various tick-borne diseases of veterinary and human significance worldwide. With advancements in molecular techniques, seven formal species of Anaplasma and numerous unclassified species have been described. In Africa, several Anaplasma species and strains have been identified in different animals and tick species. This review aims to provide an overview of the current understanding of the molecular epidemiology and genetic diversity of classified and unclassified Anaplasma species detected in animals and ticks across Africa. The review also covers control measures that have been taken to prevent anaplasmosis transmission on the continent. This information is critical when developing anaplasmosis management and control programs in Africa.

Temporal Dynamics of Anaplasma marginale Infections and the Composition of Anaplasma spp. in Calves in the Mnisi Communal Area, Mpumalanga, South Africa

Bovine anaplasmosis, caused by Anaplasma marginale, is one of the most important tick-borne diseases of cattle. Anaplasma marginale is known to be present in the Mnisi community, Mpumalanga Province, with frequent cases of anaplasmosis reported. This study investigated the infection dynamics in calves (n = 10) in two habitats in the study area over 12 months. A duplex real-time PCR assay targeting the msp1β gene of A. marginale and the groEL gene of A. centrale confirmed the presence of A. marginale in five calves in a peri-urban area from the first month, but in only two calves at the wildlife-livestock interface and only after six months. These results were confirmed by 16S rRNA microbiome analysis. Over 50 A. marginale msp1α genotypes were detected in the calves along with five novel Msp1a repeats. Calves in the peri-urban area were more likely to be infected with A. marginale than calves in the wildlife-livestock interface. Cattle management, acaricide treatment, and cattle density could explain differences in infection prevalence in the two areas. Our results revealed that most calves were superinfected by distinct A. marginale strains within the study period, indicating continuous challenge with multiple strains that should lead to robust immunity in the calves and endemic stability in the area.

Exploration and comparison of bacterial communities present in bovine faeces, milk and blood using 16S rRNA metagenomic sequencing

Cattle by-products like faeces, milk and blood have many uses among rural communities; aiding to facilitate everyday household activities and occasional rituals. Ecologically, the body sites from which they are derived consist of distinct microbial communities forming a complex ecosystem of niches. We aimed to explore and compare the faecal, milk and blood microbiota of cows through 16S rRNA sequencing. All downstream analyses were performed using applications in R Studio (v3.6.1). Alpha-diversity metrics showed significant differences between faeces and blood; faeces and milk; but non-significant between blood and milk using Kruskal-Wallis test, P < 0,05. The beta-diversity metrics on Principal Coordinate Analysis and Non-Metric Dimensional Scaling significantly clustered samples by type (PERMANOVA test, P < 0,05). The overall analysis revealed a total of 30 phyla, 74 classes, 156 orders, 243 families and 408 genera. Firmicutes, Bacteroidota and Proteobacteria were the most abundant phyla overall. A total of 58 genus-level taxa occurred concurrently between the body sites. The important taxa could be categorized into four potentially pathogenic clusters i.e. arthropod-borne; food-borne and zoonotic; mastitogenic; and metritic and abortigenic. A number of taxa were significantly differentially abundant (DA) between sites based on the Wald test implemented in DESeq2 package. Majority of the DA taxa (i.e. Romboutsia, Paeniclostridium, Monoglobus, Akkermansia, Turicibacter, Bacteroides, Candidatus_Saccharimonas, UCG-005 and Prevotellaceae_UCG-004) were significantly enriched in faeces in comparison to milk and blood, except for Anaplasma which was greatly enriched in blood and was in turn the largest microbial genus in the entire analysis. This study provides insights into the microbial community composition of the sampled body sites and its extent of overlapping. It further highlights the potential risk of disease occurrence and transmission between the animals and the community of Waaihoek in KwaZulu-Natal, Republic of South Africa pertaining to their unsanitary practices associated with the use of cattle by-products.

Epidemiology of Ticks and Tick-Borne Pathogens in Domestic Ruminants across Southern African Development Community (SADC) Region from 1980 until 2021: A Systematic Review and Meta-Analysis

Ticks are hematophagous ectoparasites that are capable of infesting a wide range of mammals, including domestic animals, ruminants, wildlife, and humans across the world, and they transmit disease-causing pathogens. Numerous individual epidemiological studies have been conducted on the distribution and prevalence of ticks and tick-borne diseases (TBDs) in the Southern African Developing Community (SADC) region, but no effort has been undertaken to synchronize findings, which would be helpful in the implementation of consolidated tick control measures. With the aim of generating consolidated pooled prevalence estimates of ticks and TBDs in the SADC region, we performed a systematic review and meta-analysis of published articles using the PRISMA 2020 guidelines. A deep search was performed on five electronic databases, namely, PubMed, ScienceDirect, Google Scholar, AJOL, and Springer Link. Of the 347 articles identified, only 61 of the articles were eligible for inclusion. In total, 18,355 tick specimens were collected, belonging to the genera Amblyomma, Haemaphysalis, Hyalomma, and Rhipicephalus (including Boophilus) across several countries, including South Africa (n = 8), Tanzania (n = 3), Zambia (n = 2), Zimbabwe (n = 2), Madagascar (n = 2), Angola (n = 2), Mozambique (n = 1), and Comoros (n = 1). The overall pooled prevalence estimate (PPE) of TBPs in livestock was 52.2%, with the highest PPE in cattle [51.2%], followed by sheep [45.4%], and goats [29.9%]. For bacteria-like and rickettsial TBPs, Anaplasma marginale had the highest PPE of 45.9%, followed by A. centrale [14.7%], A. phagocytophilum [2.52%], and A. bovis [0.88%], whilst Ehrlichia ruminantium had a PPE of 4.2%. For piroplasmids, Babesia bigemina and B. bovis had PPEs of 20.8% and 20.3%, respectively. Theileria velifera had the highest PPE of 43.0%, followed by T. mutans [29.1%], T. parva [25.0%], and other Theileria spp. [14.06%]. Findings from this study suggest the need for a consolidated scientific approach in the investigation of ticks, TBPs, and TBDs in the whole SADC region, as most of the TBDs are transboundary and require a regional control strategy.

Ticks and Tick-Borne Diseases in Cuba, Half a Century of Scientific Research

Ticks and the vast array of pathogens they transmit, including bacteria, viruses, protozoa, and helminths, constitute a growing burden for human and animal health worldwide. In Cuba, the major tropical island in the Caribbean, ticks are an important cause of vector-borne diseases affecting livestock production, pet animal health and, to a lesser extent, human health. The higher number of tick species in the country belong to the Argasidae family and, probably less known, is the presence of an autochthonous tick species in the island, Ixodes capromydis. Herein, we provide a comprehensive review of the ticks and tick-borne pathogens (TBPs) affecting animal and human health in Cuba. The review covers research results including ecophysiology of ticks, the epidemiology of TBPs, and the diagnostic tools used currently in the country for the surveillance of TBPs. We also introduce the programs implemented in the country for tick control and the biotechnology research applied to the development of anti-tick vaccines.

Molecular detection and genetic diversity of Anaplasma marginale based on the major surface protein genes in Thailand

Anaplasma marginale is the rickettsial agent of anaplasmosis, a tick-borne disease, which affects cattle and other ruminants in tropical and subtropical areas of the world, and causing huge economic losses because of decreasing meat and milk production. In the present study, molecular methods have been used to determine the occurrence and genetic diversity of A. marginale, based on the genes encoding the major surface proteins (msps) genes, in blood samples from 520 cattle and 121 buffaloes in the north and northeastern regions of Thailand. The polymerase chain reaction (PCR) results based on the msp4 gene indicated that 66 (10.30%) cattle were positive for A. marginale, whereas no positive result was obtained from buffaloes. The phylogenetic analysis based on the maximum likelihood method using 13, 29 and 27 nucleotide sequences from msp2, msp4, msp5 clones, respectively, revealed that the sequences detected in this study are obviously distributed in different clusters. The sequence analysis demonstrated that msp2 gene is genetically diverse, while msp4 and msp5 genes are conserved in Thailand. These findings corroborated the diversity analysis of the same sequences, which showed 13, 27 and 27 haplotypes of the msp2, msp4 and msp5 genes, respectively. In addition, the entropy analyses of amino acid sequences exhibited 127, 75 and 51 high entropy peaks with values ranging from 0.27119 to 2.45831, from 0.14999 to 2.17552 and from 0.15841 to 1.05453 for MSP2, MSP4 and MSP5, respectively. Therefore, the results indicate a low molecular occurrence of A. marginale in cattle blood samples in Thailand. From these results; however, a high degree of genetic diversity was observed in the analyzed A. marginale population. Hence, our finding could be used to improve the immunodiagnostics and vaccination programs for anaplasmosis.

Anaplasma marginale outer membrane protein vaccine candidates are conserved in North American and South African strains

Bovine anaplasmosis is a globally economically important tick-borne disease caused by the obligate intraerythrocytic rickettsia, Anaplasma marginale. A live Anaplasma centrale blood-based vaccine is available, but it does not protect against all A. marginale field strains and may also transmit other blood-borne pathogens. Five potential outer membrane protein (OMP) vaccine candidates have been well-characterised in A. marginale strains from the USA, however, their levels of conservation in other countries must be ascertained in order to inform their use in a vaccine with regional or global efficacy. This study assessed the amino acid variation in vaccine candidate OMPs in South African strains of A. marginale, and also compared the immunogenic properties between South African and US strains. OMP genes Am779, Am854, omp7, omp8 and omp9 were amplified and sequenced from a set of genetically diverse South African samples with different msp1α-genotypes. OMPs Am854 and Am779 were highly conserved, with 99-100 % amino acid identity, while Omp7, Omp8 and Omp9 had 79-100 % identity with US strains. As has been shown previously, Omp7-9 possess conserved N- and C- termini, a central variable region, and a highly conserved CD4 T-cell epitope, FLLVDDA(I/V)V, in the N-terminal region. Western blot analysis of recombinant OMPs indicates strong antigenic conservation between South African and US strains of A. marginale, suggesting that they are good candidates for use in a novel global vaccine cocktail, although further work on the best formulation and delivery methods will be necessary.

Epidemiology and genetic diversity of Anaplasma marginale in Zamora-Chinchipe, Ecuador

Bovine anaplasmosis, caused by the tick-borne pathogen Anaplasma marginale, is a hemolytic disease that constitutes a major constraint to cattle production in tropical and subtropical regions including Ecuador. However, the epidemiological situation of this hemoparasitosis in Ecuador is poorly characterized. The present study was aimed to determine the prevalence and genetic diversity of A. marginale in cattle of Ecuador. A cross-sectional study was carried out covering several farms from six out nine cantons of the Zamora-Chinchipe province. A total of 185 cattle were randomly selected and blood samples were collected from the animals. The studied group of animals included six breeds, three age groups, and both sexes. The molecular diagnostic was performed based on a nPCR assay targeting the A. marginale msp5 gene. Anaplasma marginale prevalence was 63.8 % and the bacteria were detected in all the cantons studied. Thirteen representative strains were selected and genetically characterized based on the msp1α gene. Genetic diversity analysis revealed that different strains circulate in the bovine herds studied. The results suggest that cattle movement may contribute to the circulation of common strains in the area. The results demonstrate a high prevalence of A. marginale in the region which should be considered by the sanitary authorities. The epidemiological surveillance for this disease should increase to anticipate acute disease outbreaks with high mortality. Bovine anaplasmosis outbreaks can cause economic losses and the death of several animals; therefore, measures for the prevention and control of this disease are required.

Molecular investigation and phylogeny of species of the Anaplasmataceae infecting animals and ticks in Senegal

BACKGROUND

Our study aimed to assess the diversity of the species of Anaplasmataceae in Senegal that infect animals and ticks in three areas: near Keur Momar Sarr (northern region), Dielmo and Diop (Sine Saloum, central region of Senegal), and in Casamance (southern region of Senegal).

METHODS

A total of 204 ticks and 433 blood samples were collected from ruminants, horses, donkeys and dogs. Ticks were identified morphologically and by molecular characterization targeting the 12S rRNA gene. Molecular characterization of species of Anaplasmataceae infecting Senegalese ticks and animals was conducted using the 23S rRNA, 16S rRNA, rpoB and groEL genes.

RESULTS

Ticks were identified as Rhipicephalus evertsi evertsi (84.3%), Hyalomma rufipes (8.3%), Hyalomma impeltatum (4.9%), R. bursa (1.5%) and R. muhsamae (0.9%). The overall prevalence of Anaplasmataceae infection in ticks was 0.9%, whereas 41.1% of the sampled animals were found infected by one of the species belonging to this family. We identified the pathogen Anaplasma ovis in 55.9% of sheep, A. marginale and A. centrale in 19.4% and 8.1%, respectively, of cattle, as well as a putative new species of Anaplasmataceae. Two Anaplasma species commonly infecting ruminants were identified. Anaplasma cf. platys, closely related to A. platys was identified in 19.8% of sheep, 27.7% of goats and 22.6% of cattle, whereas a putative new species, named here provisionally "Candidatus Anaplasma africae", was identified in 3.7% of sheep, 10.3% of goats and 8.1% of cattle. Ehrlichia canis and Anaplasma platys were identified only from dogs sampled in the Keur Momar Sarr area. Ehrlichia canis was identified in 18.8% of dogs and two R. e. evertsi ticks removed from the same sheep. Anaplasma platys was identified in 15.6% of dogs. Neither of the dogs sampled from Casamance region nor the horses and donkeys sampled from Keur Momar Sarr area were found infected by an Anaplasmataceae species.

CONCLUSIONS

This study presents a summary of Anaplasmataceae species that infect animals and ticks in three areas from the northern, central and southern regions of Senegal. To our knowledge, our findings demonstrate for the first time the presence of multiple Anaplasmataceae species that infect ticks and domestic animals in Senegal. We recorded two potentially new species commonly infecting ruminants named here provisionally as Anaplasma cf. platys and "Candidatus Anaplasma africae". However, E. canis was the only species identified and amplified from ticks. None of the other Anaplasmataceae species identified in animals were identified in the tick species collected from animals.

Genetic characterization of tick-borne pathogens in ticks infesting cattle and sheep from three South African provinces

Ticks are involved in the transmission of many public health and veterinary important pathogens. Although tick-borne pathogens are widely distributed in South Africa, information on tick-pathogen relationship needs to be updated particularly using modern molecular techniques. This study used PCR and sequencing to confirm the identity of the tick species collected from cattle and sheep from KwaZulu-Natal, Free State and Eastern Cape. Furthermore, presence of Babesia spp., Theileria spp., Anaplasma marginale, Rickettsia spp., Ehrlichia ruminantium and Coxiella burnetii was detected from tick DNA using species-specific PCR or nested PCRs. The study samples consisted of 390 adult ticks (male and female) which were pooled according to species, host animal and sampling site (three ticks per pool) for DNA extraction. The PCR results revealed that out of 130 tick DNA pools, 30 (23.1%) were positive for at least one pathogen. The most frequent pathogen was C. burnetii (9.2%), followed by Rickettsia spp. (7.7%), A. marginale (3.8%), T. mutans (3.1%), T. taurotragi (2.3%) and E. ruminantium (1.5%). The highest prevalence of pathogens was observed in ticks collected from cattle in Eastern Cape (16/42) and the lowest was in ticks obtained from sheep in Free State (1/21). Infected ticks were identified as Rhipicephalus evertsi evertsi (n = 13), R. appendiculatus (n = 3), R. decoloratus (n = 7) and Amblyomma hebraeum (n = 7). Coinfection with two pathogens was found in 21% of pathogen-positive pools. Analysis of Theileria taurotragi 18S rRNA, T. mutans 18S rRNA, C. burnetii htpB, Rickettsia spp. gltA, Rickettsia spp. ompA, E. ruminantium pCS20 and A. marginale Msp5 sequences showed that the pathogens detected in this study were genetically related to isolates previously reported in Africa. These findings provide important information on distribution of ticks and tick-borne pathogens of ruminants and will contribute in the formulation of future control strategies in South Africa.

Molecular evidence of the reservoir competence of water buffalo (Bubalus bubalis) for Anaplasma marginale in Cuba

Water buffalo (Bubalus bubalis) is a potential reservoir for Anaplasma marginale in livestock ecosystems of tropical countries. However, their participation in the epidemiological process of bovine anaplasmosis in endemic areas remains unclear. In the present study, the reservoir competence of water buffalo for A. marginale was explored by focusing on the analysis of rickettsemia levels in carrier animals, and the genetic characterization of A. marginale strains from cattle and buffalo. Eight groups of cattle and water buffaloes were randomly selected from cohabiting herds in four livestock ecosystems of Cuba, together with two control groups from unrelated cattle and buffalo herds. A total of 180 adult animals (88 water buffalo and 92 cattle) were sampled. Rickettsemia in carrier animals was determined by quantitative real-time PCR. The rickettsemia (parasitemia) levels in cattle were higher than in buffaloes, however the rickettsemia in buffalo may be enough to infect R. microplus ticks. The genetic diversity of A. marginale was assessed by strain characterization and phylogenetic analysis of 27 msp1α gene sequences. The results showed genetic similarity among strains from cattle and water buffalo, suggesting the occurrence of cross-species transmission.

Evidence confirming the phylogenetic position of Anaplasma centrale (ex Theiler 1911) Ristic and Kreier 1984

In 1911, Sir Arnold Theiler isolated and described a parasite that was very similar to Anaplasma marginale but which was more centrally located within the erythrocytes of the host cells, and was much less pathogenic than A. marginale. He named the parasite A. marginale variety centrale. The name Anaplasma centrale, referring to the same organism, was published in Validation List No. 15 in 1984, but the publication was based on an erroneous assumption that Theiler had indicated that it was a separate species. Many authors have subsequently accepted this organism as a separate species, but evidence to indicate that it is a distinct species has never been presented. The near full-length 16S rRNA gene sequence, and the deduced amino acid sequences for groEL and msp4 from several isolates of A. marginale and A. centrale from around South Africa were compared with those of the A. marginale type strain, St Maries, and the A. centrale Israel strain and other reference sequences. Phylogenetic analyses of these sequences demonstrated that A. centrale consistently forms a separate clade from A. marginale, supported by high bootstrap values (≥90 %), revealing that there is divergence between these two organisms. In addition, we discuss distinctive characteristics which have been published recently, such as differences in Msp1a/Msp1aS gene structure, as well as genome architecture that provide further evidence to suggest that A. centrale is, in fact, a separate species. Our results, therefore, provide evidence to support the existing nomenclature, and confirm that A. centrale (ex Theiler 1911) Ristic and Kreier 1984 is, indeed, a distinct species.

Detection and Characterisation of Anaplasma marginale and A. centrale in South Africa

Bovine anaplasmosis is endemic in South Africa and it has a negative economic impact on cattle farming. An improved understanding of Anaplasma marginale and Anaplasma marginale variety centrale (A. centrale) transmission, together with improved tools for pathogen detection and characterisation, are required to inform best management practices. Direct detection methods currently in use for A. marginale and A. centrale in South Africa are light microscopic examination of tissue and organ smears, conventional, nested, and quantitative real-time polymerase chain reaction (qPCR) assays, and a reverse line blot hybridisation assay. Of these, qPCR is the most sensitive for detection of A. marginale and A. centrale in South Africa. Serological assays also feature in routine diagnostics, but cross-reactions prevent accurate species identification. Recently, genetic characterisation has confirmed that A. marginale and A. centrale are separate species. Diversity studies targeting Msp1a repeats for A. marginale and Msp1aS repeats for A. centrale have revealed high genetic variation and point to correspondingly high levels of variation in A. marginale outer membrane proteins (OMPs), which have been shown to be potential vaccine candidates in North American studies. Information on these OMPs is lacking for South African A. marginale strains and should be considered in future recombinant vaccine development studies, ultimately informing the development of regional or global vaccines.

Co-infections with multiple genotypes of Anaplasma marginale in cattle indicate pathogen diversity

BACKGROUND

Only a few studies have examined the presence of Anaplasma marginale and Anaplasma centrale in South Africa, and no studies have comprehensively examined these species across the whole country. To undertake this country-wide study we adapted a duplex quantitative real-time PCR (qPCR) assay for use in South Africa but found that one of the genes on which the assay was based was variable. Therefore, we sequenced a variety of field samples and tested the assay on the variants detected. We used the assay to screen 517 cattle samples sourced from all nine provinces of South Africa, and subsequently examined A. marginale positive samples for msp1α genotype to gauge strain diversity.

RESULTS

Although the A. marginale msp1β gene is variable, the qPCR functions at an acceptable efficiency. The A. centrale groEL gene was not variable within the qPCR assay region. Of the cattle samples screened using the assay, 57% and 17% were found to be positive for A. marginale and A. centrale, respectively. Approximately 15% of the cattle were co-infected. Msp1α genotyping revealed 36 novel repeat sequences. Together with data from previous studies, we analysed the Msp1a repeats from South Africa where a total of 99 repeats have been described that can be attributed to 190 msp1α genotypes. While 22% of these repeats are also found in other countries, only two South African genotypes are also found in other countries; otherwise, the genotypes are unique to South Africa.

CONCLUSIONS

Anaplasma marginale was prevalent in the Western Cape, KwaZulu-Natal and Mpumalanga and absent in the Northern Cape. Anaplasma centrale was prevalent in the Western Cape and KwaZulu-Natal and absent in the Northern Cape and Eastern Cape. None of the cattle in the study were known to be vaccinated with A. centrale, so finding positive cattle indicates that this organism appears to be naturally circulating in cattle. A diverse population of A. marginale strains are found in South Africa, with some msp1α genotypes widely distributed across the country, and others appearing only once in one province. This diversity should be taken into account in future vaccine development studies.

Comparison of three nucleic acid-based tests for detecting <i>Anaplasma marginale</i> and <i>Anaplasma centrale</i> in cattle

Several nucleic acid-based assays have been developed for detecting Anaplasma marginale and Anaplasma centrale in vectors and hosts, making the choice of method to use in endemic areas difficult. We evaluated the ability of the reverse line blot (RLB) hybridisation assay, two nested polymerase chain reaction (nPCR) assays and a duplex real-time quantitative polymerase chain reaction (qPCR) assay to detect A. marginale and A. centrale infections in cattle (n = 66) in South Africa. The lowest detection limits for A. marginale plasmid DNA were 2500 copies by the RLB assay, 250 copies by the nPCR and qPCR assays and 2500, 250 and 25 copies of A. centrale plasmid DNA by the RLB, nPCR and qPCR assays respectively. The qPCR assay detected more A. marginale- and A. centrale-positive samples than the other assays, either as single or mixed infections. Although the results of the qPCR and nPCR tests were in agreement for the majority (38) of A. marginale-positive samples, 13 samples tested negative for A. marginale using nPCR but positive using qPCR. To explain this discrepancy, the target sequence region of the nPCR assay was evaluated by cloning and sequencing the msp1β gene from selected field samples. The results indicated sequence variation in the internal forward primer (AM100) area amongst the South African A. marginale msp1β sequences, resulting in false negatives. We propose the use of the duplex qPCR assay in future studies as it is more sensitive and offers the benefits of quantification and multiplex detection of both Anaplasma spp.

Anaplasma marginale and A. phagocytophilum in cattle in Tunisia

Background

Tick-borne diseases caused by Anaplasma species put serious constraints on the health and production of domestic cattle in tropical and sub-tropical regions. After recovering from a primary infection, cattle typically become persistent carriers of pathogens and play a critical role in the epidemiology of the disease, acting as reservoirs of the Anaplasma spp.

Methods

In this study a duplex PCR assay was used for the simultaneous detection of Anaplasma marginale and Anaplasma phagocytophilum in cattle using two primer pairs targeting msp4 and msp2 genes, respectively. We used this method to analyze DNA preparations derived from 328 blood cattle samples that were collected from 80 farms distributed among Tunisia’s four bioclimatic zones.

Results

The prevalence of the A. marginale infection (24.7 %) was significantly higher and more widespread (in all bioclimatic areas) than that of A. phagocytophilum (0.6 %), which was found in a mixed infection with A. marginale.

Conclusions

The duplex PCR assay used proved to be a rapid, specific and inexpensive mean for the simultaneous detection of Anaplasma marginale and Anaplasma phagocytophilum in cattle blood. It allowed us to report the identification of A. phagocytophilum for the first time in cattle in Tunisia and confirm the presence of A. marginale in cattle from several geographical areas of the country. Further epidemiological studies undertaken using this assay will help improve the surveillance of the associated diseases in the regions where they are endemic.

Characterization of Anaplasma marginale subsp. centrale Strains by Use of msp1aS Genotyping Reveals a Wildlife Reservoir

Bovine anaplasmosis caused by the intraerythrocytic rickettsial pathogen Anaplasma marginale is endemic in South Africa. Anaplasma marginale subspecies centrale also infects cattle; however, it causes a milder form of anaplasmosis and is used as a live vaccine against A. marginale There has been less interest in the epidemiology of A. marginale subsp. centrale, and, as a result, there are few reports detecting natural infections of this organism. When detected in cattle, it is often assumed that it is due to vaccination, and in most cases, it is reported as coinfection with A. marginale without characterization of the strain. A total of 380 blood samples from wild ruminant species and cattle collected from biobanks, national parks, and other regions of South Africa were used in duplex real-time PCR assays to simultaneously detect A. marginale and A. marginale subsp. centrale. PCR results indicated high occurrence of A. marginale subsp. centrale infections, ranging from 25 to 100% in national parks. Samples positive for A. marginale subsp. centrale were further characterized using the msp1aS gene, a homolog of msp1α of A. marginale, which contains repeats at the 5' ends that are useful for genotyping strains. A total of 47 Msp1aS repeats were identified, which corresponded to 32 A. marginale subsp. centrale genotypes detected in cattle, buffalo, and wildebeest. RepeatAnalyzer was used to examine strain diversity. Our results demonstrate a diversity of A. marginale subsp. centrale strains from cattle and wildlife hosts from South Africa and indicate the utility of msp1aS as a genotypic marker for A. marginale subsp. centrale strain diversity.

Anaplasma marginale: Diversity, Virulence, and Vaccine Landscape through a Genomics Approach

In order to understand the genetic diversity of A. marginale, several efforts have been made around the world. This rickettsia affects a significant number of ruminants, causing bovine anaplasmosis, so the interest in its virulence and how it is transmitted have drawn interest not only from a molecular point of view but also, recently, some genomics research have been performed to elucidate genes and proteins with potential as antigens. Unfortunately, so far, we still do not have a recombinant anaplasmosis vaccine. In this review, we present a landscape of the multiple approaches carried out from the genomic perspective to generate valuable information that could be used in a holistic way to finally develop an anaplasmosis vaccine. These approaches include the analysis of the genetic diversity of A. marginale and how this affects control measures for the disease. Anaplasmosis vaccine development is also reviewed from the conventional vaccinomics to genome-base vaccinology approach based on proteomics, metabolomics, and transcriptomics analyses reported. The use of these new omics approaches will undoubtedly reveal new targets of interest in the near future, comprising information of potential antigens and the immunogenic effect of A. marginale proteins.

RepeatAnalyzer: a tool for analysing and managing short-sequence repeat data

Background

Short-sequence repeats (SSRs) occur in both prokaryotic and eukaryotic DNA, inter- and intragenically, and may be exact or inexact copies. When heterogeneous SSRs are present in a given locus, we can take advantage of the pattern of different repeats to genotype strains based on the SSRs. Cataloguing and tracking these repeats can be difficult as diverse groups of researchers are involved in the identification of the repeats. Additionally, the task is error-prone when done manually.

Results

We developed RepeatAnalyzer, a new software tool capable of tracking, managing, analysing and cataloguing SSRs and genotypes using Anaplasma marginale as a model species. RepeatAnalyzer’s analysis capability includes novel metrics for measuring regional genetic diversity (corresponding to variety and regularity of SSR occurrence). As a part of its visualization capabilities, RepeatAnalyzer produces high quality maps of the geographic distribution of genotypes or SSRs over a region of interest. RepeatAnalyzer’s repeat identification functionality was validated for all SSRs and genotypes reported in 21 publications, using 380 A. marginale isolates gathered from the five publications within that list that provided access to their isolates. The tool produced accurate genotyping results in every case. In addition, it uncovered a number of errors in the published literature: 11 cases where SSRs were misreported, 5 cases where two different SSRs had been given the same name, and 16 cases where two or more names had been given to a single SSR. The analysis and visualization functionalities of the tool are demonstrated using several examples.

Conclusions

RepeatAnalyzer is a robust software tool that can be used for storing, managing, and analysing short-sequence repeats for the purpose of strain identification. The tool can be used for any set of SSRs regardless of species. When applied to A. marginale, our test case, we show that genotype lengths for a given region follow a normal distribution, while SSR frequencies follow a power-law-like distribution. Further, we find that over 90 % of repeats are 28 to 29 amino acids long, which is in agreement with conventional wisdom. Lastly, our analysis reveals that the most common edit distance is five or six, which is counter-intuitive since we expected that result to be closer to one, resulting from the simplest change from one repeat to another.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2686-2) contains supplementary material, which is available to authorized users.

Alpha proteobacteria of genusAnaplasma(Rickettsiales: Anaplasmataceae): Epidemiology and characteristics ofAnaplasmaspecies related to veterinary and public health importance

TheAnaplasmaspecies are important globally distributed tick-transmitted bacteria of veterinary and public health importance. These pathogens, cause anaplasmosis in domestic and wild animal species including humans.Rhipicephalus, Ixodes, DermacentorandAmblyommagenera of ticks are the important vectors ofAnaplasma.Acute anaplasmosis is usually diagnosed upon blood smear examination followed by antibodies and nucleic acid detection. All age groups are susceptible but prevalence increases with age. Serological cross-reactivity is one of the important issues amongAnaplasmaspecies. They co-exist and concurrent infections occur in animals and ticks in same geographic area. These are closely related bacteria and share various common attributes which should be considered while developing vaccines and diagnostic assays. Movement of susceptible animals from non-endemic to endemic regions is the major risk factor of bovine/ovine anaplasmosis and tick-borne fever. Tetracyclines are currently available drugs for clearance of infection and treatment in humans and animals. Worldwide vaccine is not yet available. Identification, elimination of reservoirs, vector control (chemical and biological), endemic stability, habitat modification, rearing of tick resistant breeds, chemotherapy and tick vaccination are major control measures of animal anaplasmosis. Identification of reservoirs and minimizing the high-risk tick exposure activities are important control strategies for human granulocytic anaplasmosis.

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.

Characterization of two strains of Anaplasma marginale isolated from cattle in Rio de Janeiro, Brazil, after propagation in tick cell culture

IDE8 tick cell cultures have been used for the isolation and propagation of several isolates of Anaplasma marginale. The genetic heterogeneity of A. marginale strains in cattle is diverse in endemic regions worldwide and the analyses of msp1α (major surface protein 1 alpha) gene sequences have allowed the identification of different strains. This study reports the isolation and propagation of two new isolates of A. marginale in IDE8 cells from blood of two cattle and their morphological and molecular characterization using light microscopy and the msp1α gene, respectively. Small colonies were observed in cytospin smears of each of the isolates 60 days after culture initiation. Based on msp1α sequence variation, the two isolates were found to be separate strains and were named AmRio1 and AmRio2. Analysis of msp1α microsatellite in both strains resulted in a single genotype, genotype E. The amino acid sequence of one MSP1α tandem repeat from the strain AmRio1 resulted in a new sequence (named 162) with one amino acid change. The results of these phylogenetic analyses demonstrated that A. marginale strains from Brazil and Argentina formed two large clusters of which one was less divergent that the other.