Molecular epidemiology of anaplasmosis in small ruminants along a human-livestock-wildlife interface in Uganda

Occurrence and molecular prevalence of Anaplasmataceae, Rickettsiaceae and Coxiellaceae in African wildlife: A systematic review and meta-analysis

INTRODUCTION

Tick-borne pathogens (TBPs) constitute an emerging threat to public and animal health especially in the African continent, where land-use change, and wildlife loss are creating new opportunities for disease transmission. A review of TBPs with a focus on ticks determined the epidemiology of Rhipicephalus ticks in heartwater and the affinity of each Rickettsia species for different tick genera. We conducted a systematic review and meta-analysis to collect, map and estimate the molecular prevalence of Anaplasmataceae, Rickettsiaceae and Coxiellaceae in African wildlife.

MATERIALS AND METHODS

Relevant scientific articles were retrieved from five databases: PubMed, ScienceDirect, Scopus, Ovid and OAIster. Publications were selected according to pre-determined exclusion criteria and evaluated for risk of bias using the appraisal tool for cross-sectional studies (AXIS). We conducted an initial descriptive analysis followed by a meta-analysis to estimate the molecular prevalence of each pathogen. Subgroup analysis and meta-regression models were employed to unravel associations with disease determinants. Finally, the quality of evidence of every estimate was finally assessed.

RESULTS

Out of 577 retrieved papers, a total of 41 papers were included in the qualitative analysis and 27 in the meta-analysis. We retrieved 21 Anaplasmataceae species, six Rickettsiaceae species and Coxiella burnetii. Meta-analysis was performed for a total of 11 target pathogens. Anaplasma marginale, Ehrlichia ruminantium and Anaplasma centrale were the most prevalent in African bovids (13.9 %, CI: 0-52.4 %; 20.9 %, CI: 4.1-46.2 %; 13.9 %, CI: 0-68.7 %, respectively). Estimated TBPs prevalences were further stratified per animal order, family, species and sampling country.

DISCUSSION

We discussed the presence of a sylvatic cycle for A. marginale and E. ruminantium in wild African bovids, the need to investigate A. phagocytophilum in African rodents and non-human primates as well as E. canis in the tissues of wild carnivores, and a lack of data and characterization of Rickettsia species and C. burnetii.

CONCLUSION

Given the lack of epidemiological data on wildlife diseases, the current work can serve as a starting point for future epidemiological and/or experimental studies.

Molecular detection and associated risk factors of Anaplasma marginale, A. ovis and A. platys in sheep from Algeria with evidence of the absence of A. phagocytophilum

Anaplasma species are obligate intracellular rickettsial pathogens that cause significant diseases in animals and humans. Despite their importance, limited information on Anaplasma infections in Algeria has been published thus far. This study aimed to assess the infection rate, characterize Anaplasma species, and identify associated risk factors in selected sheep farms across Oum El Bouaghi region in Algeria. In 2018, we collected 417 blood samples from sheep (Ovis aries) and performed molecular characterization of Anaplasma species infecting these animals. This characterization involved the use of 16S rRNA, msp2, rpoB, and msp5 genes, which were analyzed through nested PCR, qPCR, cPCR, DNA sequencing, and subsequent phylogenetic analysis. Our findings revealed infection rates of 12.7 % for Anaplasma species detected, with Anaplasma ovis at 10.8 %, Anaplasma marginale at 1.7 %, and Anaplasma platys at 0.2 %. Interestingly, all tested animals were found negative for Anaplasma phagocytophilum. Statistical analyses, including the Chi-square test and Fisher exact test, failed to establish any significant relationships (p > 0.05) between A. ovis and A. platys infections and variables such as age, sex, sampling season, and tick infestation level. However, A. marginale infection exhibited a significant association with age (p < 0.05), with a higher incidence observed in lambs (5.2 %) compared to other age groups. Remarkably, this study represents the first molecular detection of A. platys and A. marginale in Algerian sheep. These findings suggest that Algerian sheep may serve as potential reservoirs for these pathogens. This research contributes valuable insights into the prevalence and characteristics of Anaplasma infections in Algerian sheep populations, emphasizing the need for further investigation and enhanced surveillance to better understand and manage these diseases.

Hard ticks (Acari: Ixodidae) and tick-borne diseases of sheep and goats in Africa: A review

Ticks are leading vectors of economically important pathogens that affect small ruminants due to favourable climatic conditions across different regions of the African continent. They are responsible for both direct and indirect economic losses in the livestock industry. This review focuses on the species diversity of hard ticks, their biology, tick-borne diseases of sheep and goats including non-infectious disease, and risk factors to tick infestation in Africa. Furthermore, our review provides recent updates on distribution of ticks and tick-borne pathogens of small ruminants in Africa. It was observed that several species and subspecies of hard ticks belonging to the genera Hyalomma (Hy), Rhipicephalus (Rh), Ixodes (I) and Amblyomma (Am) were found infesting small ruminants across the different regions of the continent. Of these genera, Rhipicephalus ticks accounts for the majority of the registered species, with exactly 27 different species infesting small ruminant stocks comprising of different developmental instars and adults of the tick. Rhipicephalus decolaratus, Rh. e. evertsi and Rh. appendiculatus were the three most common Rhipicephalus species reported. Both protozoal (Babesia and Theileria) and bacterial (Anaplasma, Rickettsia, Ehrlichia, Coxiella and Mycoplasma) pathogens have being reported to be amplified in several hard tick species and/or small ruminant hosts. Furthermore, tick paralysis and lameness were non-infectious conditions attributed to tick infestations. Amblyomma hebraeum and Rh. glabroscutatum may cause lameness in goats, while Hy. rufipes is responsible for the same condition in Merino sheep. Host paralysis due to a neurotoxin released by female Rh. e. evertsi and I. rubicundus has been documented within the continent. We therefore advocate for the need of integrated control measures against tick-borne pathogens (TBPs) including their arthropod vectors, to be performed simultaneously to ease the burden of vector-borne diseases in small ruminant production.

Molecular prevalence and associated infection risk factors of tick-borne protozoan and rickettsial blood pathogens in small ruminants

BACKGROUND

Tick-borne blood pathogens cause highly pathogenic diseases, which are associated with substantial economic losses in ruminants. Despite this, epidemiological research on these pathogens remains neglected in many countries. This study initiated a regional epidemiological survey that included the detection of molecular prevalence, associated risk factors, and gene sequencing, combined with phylogenetic analysis, targeting the two main tick-borne blood protozoan and rickettsial pathogens of Babesia, Theileria, and Anaplasma that infect small ruminants. One hundred blood samples were collected from 76 sheep and 24 goats.

RESULTS

Microscopic examination of Giemsa-stained blood films revealed that 73% of the samples were infected with at least one species of the three blood pathogenic organisms. Molecular diagnosis based on the 18 S rRNA for Babesia and Theileria species and the major surface protein 4 (msp4) for Anaplasma species, revealed that 43% of the small ruminants were infected with at least one of these pathogens. The animal's sex was the most significant associated risk factor, with 49.4% of female animals infected compared with only 4% of male animals (P < 0.05). The open breeding system recorded the highest infection rate for tick-borne blood pathogens. Homology-based and phylogenetic analyses indicated that the specific isolate species were Babesia ovis (B. ovis), Theileria ovis (T. ovis), and Anaplasma ovis (A. ovis), with sequences showing significant identities with isolates from sheep, goats, and other animal species, and geographically diverse countries in Africa, Asia, and Europe, in addition to Egypt.

CONCLUSION

This was the first molecular evidence of B. ovis, T. ovis, and A. ovis infections in sheep and goat populations in the North Coast region of Egypt. More extensive studies are required to develop an epidemiological map of blood pathogenic organisms, while more effective control strategies are required to reduce the burden of tick-borne pathogens on small ruminants.

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.

Molecular survey of Anaplasma and Ehrlichia species in livestock ticks from Kassena-Nankana, Ghana; with a first report of Anaplasma capra and Ehrlichia minasensis

Tick-borne pathogens harm livestock production and pose a significant risk to public health. To combat these effects, it is necessary to identify the circulating pathogens to create effective control measures. This study identified Anaplasma and Ehrlichia species in ticks collected from livestock in the Kassena-Nankana Districts between February 2020 and December 2020. A total of 1550 ticks were collected from cattle, sheep and goats. The ticks were morphologically identified, pooled and screened for pathogens using primers that amplify a 345 bp fragment of the 16SrRNA gene and Sanger sequencing. The predominant tick species collected was Amblyomma variegatum (62.98%). From the 491 tick pools screened, 34 (6.92%) were positive for Ehrlichia and Anaplasma. The pathogens identified were Ehrlichia canis (4.28%), Ehrlichia minasensis (1.63%), Anaplasma capra (0.81%) and Anaplasma marginale (0.20%). This study reports the first molecular identification of the above-mentioned Ehrlichia and Anaplasma species in ticks from Ghana. With the association of human infections with the zoonotic pathogen A. capra, livestock owners are at risk of infections, calling for the development of effective control measures.

First molecular identification of multiple tick-borne pathogens in livestock within Kassena-Nankana, Ghana

The risk of pathogen transmission continues to increase significantly in the presence of tick vectors due to the trade of livestock across countries. In Ghana, there is a lack of data on the incidence of tick-borne pathogens that are of zoonotic and veterinary importance. This study, therefore, aimed to determine the prevalence of such pathogens in livestock using molecular approaches. A total of 276 dry blood spots were collected from cattle (100), sheep (95) and goats (81) in the Kassena-Nankana Districts. The samples were analyzed using Polymerase Chain Reaction (qPCR) and conventional assays and Sanger sequencing that targeted pathogens including Rickettsia, Coxiella, Babesia, Theileria, Ehrlichia and Anaplasma. An overall prevalence of 36.96% was recorded from the livestock DBS, with mixed infections seen in 7.97% samples. Furthermore, the prevalence of infections in livestock was recorded to be 19.21% in sheep, 14.13% in cattle, and 3.62% in goats. The pathogens identified were Rickettsia spp. (3.26%), Babesia sp. Lintan (8.70%), Theileria orientalis (2.17%), Theileria parva (0.36%), Anaplasma capra (18.48%), Anaplasma phagocytophilum (1.81%), Anaplasma marginale (3.26%) and Anaplasma ovis (7.25%). This study reports the first molecular identification of the above-mentioned pathogens in livestock in Ghana and highlights the use of dry blood spots in resource-limited settings. In addition, this research provides an update on tick-borne pathogens in Ghana, suggesting risks to livestock production and human health. Further studies will be essential to establish the distribution and epidemiology of these pathogens in Ghana.

Molecular survey for tick-borne pathogens and associated risk factors in sheep and goats in Kano Metropolis, Nigeria

Tick-borne pathogens (TBPs) pose an increased health and productivity risk to livestock in sub-Saharan Africa. Information regarding TBPs infecting small ruminants in Kano metropolis is scarce. Therefore, we investigated the molecular epidemiology of tick-borne pathogens of economic importance from sheep and goats in Kano, Nigeria using Polymerase chain reaction (PCR). A total of 346 blood DNA samples were collected from small ruminants and analyzed for TBPs using PCR and sequencing. Risk of infection was determined for age, sex, breed and animal species. Our results indicate the absence of piroplasmids (Babesia/Theileria) and Rickettsia spp. infections. The overall prevalence for Anaplasma spp. was 9.25% (32/346) with a higher prevalence in goats 13.59% (25/184) compared with sheep 4.32% (7/162). With respect to age of animals, goats >4 years had the highest prevalence of 32.45% (11/37) which differs significantly (P = 0.0059) compared with other age categories. Cross breed goats had a prevalence of 15.63% (5/32) compared with Kano brown breed 14.08 (20/142). Sex significant difference (P = 0.029) was observed in the goats with females having the highest prevalence 20.89% (14/67) compared with males 9.40% (11/117). Furthermore, with regards to sheep, no significant difference (P > 0.05) was observed with respect to age and breed. Finally, no significant difference (P > 0.05) was observed with the prevalence of Anaplasma spp. due to Body condition score (BCS) in both sheep and goats. Conclusively, the occurrence of TBPs in small ruminants is low. Continuous efforts in tick control must be sustained to ensure high productive yield and reduced disease burden associated with TBPs of sheep and goats in Kano metropolis.

The first study on the seroprevalence of Anaplasma spp. in small ruminants and assessment of associated risk factors in North Egypt

Background and Aim

Ovine anaplasmosis is a rickettsial disease caused by Anaplasma spp. These Gram-negative intracellular bacteria are mainly transmitted by ticks and infected blood cells of caprine, ovine, and wild small ruminants. At present, epidemiological data on anaplasmosis in cattle, dogs, and camels in Egypt are available, but the data about Anaplasma spp. in sheep and goat are scarce. This study aimed to determine the seroprevalence of Anaplasma spp. in small ruminants and assess the associated risk factors.

Materials and Methods

A cross-sectional study was performed to investigate the seroprevalence of Anaplasma spp. in 300 sheep and 300 goats from four governorates in North Egypt using a commercial competitive enzyme-linked immunosorbent assays kit, and the associated risk factors for the infection were evaluated.

Results

Overall, the seroprevalence of anti-Anaplasma antibodies was 18.3% and 21.3% in sheep and goats, respectively. A multivariable logistic regression model was used to determine the association between risk factors and Anaplasma spp. infection.

Conclusion

Age, animal husbandry, acaricide use, tick infestation, and contact with cattle were the primary risk factors for Anaplasma seropositivity. This study confirms the presence of antibodies against Anaplasma spp. in small ruminants from Egypt. This is the first study to assess the associated risk factors for Anaplasma infection in small ruminants from Egypt. Further studies are needed to improve the understanding of the associated disease factors, facilitating the development of new procedures for control of anaplasmosis in livestock.

Cattle ticks and tick-borne diseases: a review of Uganda's situation

Herein we review the epidemiology of ticks and tick-borne diseases (TTBDs), their impact on livestock health and on the economy, control and associated challenges in Uganda. Ticks are leading vectors of economically important pathogens and are widespread in Uganda due to suitable climatic conditions. Besides the physical injury inflicted on the animal host, ticks transmit a number of pathogens that can cause morbidity and mortality of livestock if untreated, resulting in economic losses. Uganda suffers an aggregated annual loss (direct and indirect) of over USD 1.1 billion in the TTBDs complex. East Coast fever (ECF) caused by a protozoan haemoparasite, Theileria parva, is the most prevalent and economically important tick-borne disease (TBD) in Uganda and its vector, the brown ear tick (Rhipicephalus appendiculatus) widely distributed. Other prevalent TBDs in Uganda include anaplasmosis, babesiosis and heartwater. We highlight the role of agro-ecological zones (AEZs) and livestock management system in the distribution of TTBDs, citing warm and humid lowlands as being ideal habitats for ticks and endemic for TBDs. Control of TTBDs is a matter of great importance as far as animal health is concerned in Uganda. Indigenous cattle, which make up over 90% of the national herd are known to be more tolerant to TTBDs and most farms rely on endemic stability to TBDs for control. However, exotic cattle breeds are more capital intensive than indigenous breeds, but the increasing adoption of tick-susceptible exotic cattle breeds (especially dairy) in western and central Uganda demands intensive use of acaricides for tick control and prevention of TBDs. Such acaricide pressure has unfortunately led to selection of acaricide-resistant tick populations and the consequent acaricide resistance observed in the field. Vaccination against ECF, selective breeding for tick resistance and integrated tick control approaches that limit tick exposure, could be adopted to interrupt spread of acaricide resistance. We recommend increasing monitoring and surveillance for TTBDs and for emerging acaricide resistance, improved extension services and sensitization of farmers on tick control measures, appropriate acaricide use and the development and implementation of vaccines for the control of TTBDs as more sustainable and effective interventions. A tick control policy should be developed, taking into account variations of agro-ecological zones, farm circumstances and indigenous technical knowledge, and this should be incorporated into the overall animal health program.