First molecular evidence of Babesia occultans and Theileria separata infection in ticks and sheep in China

An Update of Evidence for Pathogen Transmission by Ticks of the Genus Hyalomma

Current and likely future changes in the geographic distribution of ticks belonging to the genus Hyalomma are of concern, as these ticks are believed to be vectors of many pathogens responsible for human and animal diseases. However, we have observed that for many pathogens there are no vector competence experiments, and that the level of evidence provided by the scientific literature is often not sufficient to validate the transmission of a specific pathogen by a specific Hyalomma species. We therefore carried out a bibliographical study to collate the validation evidence for the transmission of parasitic, viral, or bacterial pathogens by Hyalomma spp. ticks. Our results show that there are very few validated cases of pathogen transmission by Hyalomma tick species.

The Common Occurrence of Theileria ovis in Tibetan Sheep and the First Report of Theileria sinensis in Yaks from Southern Qinghai, China

PURPOSE

The tick-borne protozoa piroplasms, including Theileria and Babesia, are the cause of substantial economic losses to the livestock industry. However, in southern Qinghai province, China, there are limited information on the molecular characteristics of piroplasms. This study therefore aimed at determining the prevalence and genetic diversity of piroplasms.

METHODS

In order to detect piroplasms, we examined 330 yaks and 236 Tibetan sheep blood samples by nested PCR. The differences in piroplasms prevalence in relation to different risk factors was analyzed using SPSS 26. Phylogenetic analysis based on 18S rRNA sequences was inferred using MEGA 7.

RESULTS

During this study, Theileria spp. were detected in 33.6% (111/330) of yaks and 94.1% (222/236) of Tibetan sheep, but no Babesia was identified. Importantly, a comparison study revealed that T. ovis infection was highly prevalent in sheep (94.1%) but infrequent in yaks (6.1%), while T. sinensis was host-specific to yaks with an infection rate of 27.6%. In addition, male animals were more likely to be infected by T. sinensis and female animals were more likely to be infected by T. ovis. And animals below 4000 m areas reported a higher infection rate with T. sinensis (26.1% vs. 2.9%, p < 0.001). Alongside these differences in prevalence, we found a significantly higher T. sinensis infection rate in separated-grazing livestock (22.2% vs. 3.7%, p < 0.001), while mixed-grazing ruminants had a higher T. ovis infection rate (50.0% vs. 39.0%, p = 0.014). Furthermore, sequence analysis revealed that the 18S rRNA sequences obtained in this study shared 86.9-100.0% identities with each other and they were clustered into T. sinensis or T. ovis.

CONCLUSION

To our knowledge, this is the first report of T. sinensis in Qinghai region. In addition, high prevalence of the generally sub-clinical T. ovis in sheep indicates extensive exposure to ticks and transmission of tick-borne pathogens with a significant economic impact. This study provides insights into the distribution and genetic diversity of Theileria in China.

Babesiosis as a potential threat for bovine production in China

Babesiosis is a tick-borne disease with global impact caused by parasites of the phylum Apicomplexa, genus Babesia. Typically, acute bovine babesiosis (BB) is characterized by fever, anemia, hemoglobinuria, and high mortality. Surviving animals remain persistently infected and become reservoirs for parasite transmission. Bovids in China can be infected by one or more Babesia species endemic to the country, including B. bovis, B. bigemina, B. orientalis, B. ovata, B. major, B. motasi, B. U sp. Kashi and B. venatorum. The latter may pose a zoonotic risk. Occurrence of this wide diversity of Babesia species in China may be due to a combination of favorable ecological factors, such as the presence of multiple tick vectors, including Rhipicephalus and Hyalomma, the coexistence of susceptible bovid species, such as domestic cattle, yaks, and water buffalo, and the lack of efficient measures of tick control. BB is currently widespread in several regions of the country and a limiting factor for cattle production. While some areas appear to have enzootic stability, others have considerable cattle mortality. Research is needed to devise solutions to the challenges posed by uncontrolled BB. Critical research gaps include risk assessment for cattle residing in endemic areas, understanding factors involved in endemic stability, evaluation of parasite diversity and pathogenicity of regional Babesia species, and estimation of whether and how BB should be controlled in China. Research should allow the design of comprehensive interventions to improve cattle production, diminish the risk of human infections, and increase the availability of affordable animal protein for human consumption in China and worldwide. In this review, we describe the current state of BB with reference to the diversity of hosts, vectors, and parasite species in China. We also discuss the unique risks and knowledge gaps that should be taken into consideration for future Babesia research and control strategies.

First report of Babesia occultans in two symptomatic cows in Iran

This study reports the identification and first molecular characterization of Babesia occultans from naturally infected cows in Iran. Microscopic examination showed pyriform trophozoites, and ring-shaped merozoites (>2.5 μm) in Giemsa-stained blood smears obtained from two symptomatic cows in West-Azarbaijan province, Iran. PCR amplification of the partial 18S rRNA gene including the V4 hypervariable region were carried out on DNA extracted from blood samples. BLAST analyses of the partial 18S rRNA (approximately 400 bp) obtained from two cows revealed the presence of B. occultans and the detected sequences were identical to each other. Comparisons of the partial 18S rRNA sequence of the current isolate with other B. occultans sequences from Tunisia, South Africa, Turkey, Pakistan, and China confirmed the relation of the Iranian isolate to the species B. occultans. Sequence analysis of the obtained B. occultans showed 99.5-100% identity to the previously reported isolates. The sequences of B. occultans had 100% identity to a sequence obtained from ticks in Tunisia. This report is the beginning of a path to further research about B. occultans in vectors and reservoirs throughout Iran.

Molecular Detection and Identification of Babesia spp., Theileria spp., and Anaplasma spp. in Sheep From Border Regions, Northwestern China

Babesia, Theileria, and Anaplasma are important causative agents of tick-borne diseases that severely affect sheep. However, there is paucity in the occurrence genetic diversity of the infections of tick-borne diseases in sheep in border regions, northwestern China. In this study, nested polymerase chain reaction (nPCR) assays and gene sequencing were used to identify tick-borne Babesia spp., Theileria spp., and Anaplasma spp. infections in border regions, northwestern China. Out of 323 samples tested in this study, 225 (69.7%) sheep were infected with Babesia spp., Theileria spp., and Anaplasma spp. Two hundred six (63.8%), 60 (18.6%), 54 (16.7%), 51 (15.8%), 32 (9.9%), 19 (5.9%), and 16 (5.0%) were positive for A. ovis, B. motasi-like, A. bovis, T. uilenbergi, A. phagocytophilum, T. luwenshuni, and B. motasi-like Xinjiang, respectively. The most common dual infection was with A. ovis and B. motasi-like while the most frequent triple coinfection was A. ovis, B. motasi-like, and T. uilenbergi with coinfection rates of 17.0% (55/323) and 5.0% (16/323), respectively. Sequencing analysis indicated that A. ovis MSP4, A. phagocytophilum epank1, A. bovis 16S rRNA, B. motasi-like rap1-b, B. motasi-like Xinjiang rap1-a, T. luwenshuni 18S rRNA, and T. uilenbergi 18S rRNA from border regions, northwestern China, showed 99–100% identity with documented isolates from other countries. To the best of the authors' knowledge, this is the first report of T. uilenbergi and T. luwenshuni infections of sheep in border regions, northwestern China. Furthermore, these findings provide important data for understanding the distribution of Babesia, Theileria, and Anaplasma in sheep between border countries and China.

Highlights of Veterinary Entomology, 2019

Research in the field of veterinary entomology is dominated by studies concerning arthropods that affect animal health. In 2019, this research primarily addressed the overwhelming industry need to manage detrimental species such as biting flies and ticks and the ongoing problems caused by insecticide/acaricide resistance evolution in these pests. Research also included evidence supporting the need for the conservation of beneficial species, such as biological control organisms. Many studies in a variety of pest systems have demonstrated the potential detrimental effects of insecticide use on nontarget organisms, and those of veterinary importance are no exception. An emphasis also was placed on research regarding alternative management strategies for veterinary pests. The presentation herein provides a descriptive summary of selected research that contributed greatly to the body of knowledge regarding arthropods of veterinary importance. This included several studies that will pave the way towards more effective veterinary pest management in an effort to improve animal health and welfare and, therefore, the sustainability of animal agriculture.

Prevalence and molecular characterization of ticks and tick-borne pathogens of one-humped camels (Camelus dromedarius) in Nigeria

Background

Ticks are hematophagous arthropods responsible for maintenance and transmission of several pathogens of veterinary and medical importance. Current knowledge on species diversity and pathogens transmitted by ticks infesting camels in Nigeria is limited. Therefore, the aim of this study was to unravel the status of ticks and tick-borne pathogens of camels in Nigeria.

Methods

Blood samples (n = 176) and adult ticks (n = 593) were collected from one-humped camels (Camelus dromedarius) of both sexes in three locations (Kano, Jigawa and Sokoto states) in north-western Nigeria and screened for the presence of Rickettsia spp., Babesia spp., Anaplasma marginale, Anaplasma spp. and Coxiella-like organisms using molecular techniques. All ticks were identified to species level using a combination of morphological and molecular methods.

Results

Ticks comprised the three genera Hyalomma, Amblyomma and Rhipicephalus. Hyalomma dromedarii was the most frequently detected tick species (n = 465; 78.4%) while Amblyomma variegatum (n = 1; 0.2%) and Rhipicephalus evertsi evertsi (n = 1; 0.2%) were less frequent. Other tick species included H. truncatum (n = 87; 14.7%), H. rufipes (n = 19; 3.2%), H. impeltatum (n = 18; 3.0%) and H. impressum (n = 2; 0.3%). The minimum infection rates of tick-borne pathogens in 231 tick pools included Rickettsia aeschlimannii (n = 51; 8.6%); Babesia species, (n = 4; 0.7%) comprising of B. occultans (n = 2), B. caballi (n = 1) and Babesia sp. (n = 1); Coxiella burnetii (n = 17; 2.9%); and endosymbionts in ticks (n = 62; 10.5%). We detected DNA of “Candidatus Anaplasma camelli” in 40.3% of the blood samples of camels. Other tick-borne pathogens including Anaplasma marginale were not detected. Analysis of risk factors associated with both tick infestation and infection with Anaplasma spp. in the blood indicated that age and body condition scores of the camels were significant (P < 0.05) risk factors while gender was not.

Conclusions

This study reports low to moderate prevalence rates of selected tick-borne pathogens associated with camels and their ticks in north-western Nigeria. The presence of zoonotic R. aeschlimannii emphasizes the need for a concerted tick control programme in Nigeria.

Bovine ticks harbour a diverse array of microorganisms in Pakistan

BACKGROUND

Ticks and tick-borne pathogens (TTBP) are a major constraint to livestock production in Pakistan; despite a high prevalence of TTBPs, knowledge on the capacity of Pakistani ticks to carry pathogens and endosymbionts is limited. Furthermore, mixed infections with multiple microorganisms further complicate and limit the detection potential of traditional diagnostic methods. The present study investigated the tick-borne microorganisms in bovine ticks in Pakistan, employing a high-throughput microfluidic real-time PCR based technique.

METHODS

Ticks were collected from clinically healthy cattle (n = 116) and water buffaloes (n = 88) from 30 villages across six districts located in five agro-ecological zones (AEZs) of Pakistan from September to November 2017. The microfluidic real-time PCR was used to test the genomic DNA of individual ticks for the presence of 27 bacterial and eight parasitic microorganisms. Phylogenetic methods were used to assess the genetic relationship of DNA sequences determined herein.

RESULTS

PCR detected DNA of at least one microorganism in each of 221 ticks tested (94.4%, 221/234). DNA-based detection inferred that single pathogens/endosymbionts were the most common (43.4%, 96/221) followed by double (38.9%, 86/221), triple (14.5%, 32/221), quadruple (2.3%, 5/221) and quintuple (0.9%, 2/221) mixed infections. Piroplasms (Babesia/Theileria spp.) were the most prevalent (31.6%, 74/234), followed by Ehrlichia spp. (20%, 47/234) and Anaplasma marginale (7.7%, 18/234). Anaplasma phagocytophilum, A. ovis, A. centrale, Babesia ovis, Borrelia spp., Rickettsia spp., R. massiliae, Bartonella spp. and Hepatozoon spp. were also detected. Endosymbionts such as Francisella-like (91.5%, 214/234) and Coxiella-like (1.3%, 3/234) organisms were also detected in ticks. The highest diversity of microorganisms was detected in Hyalomma anatolicum ticks (test-positive for 14/14 microorganisms), followed by Rhipicephalus microplus (4/14), Hy. hussaini (3/14) and Rh. annulatus (2/14). Ticks collected from cattle carried significantly more frequently piroplasms (41.2%, 54/131; P < 0.05) than those from buffaloes (19.4%, 20/103). However, the overall prevalence of microorganisms did not vary significantly among ticks from the two host species as well as across different AEZs.

CONCLUSIONS

To our knowledge, this is the first study to investigate a wide range of tick-borne microorganisms in bovine ticks using a high-throughput diagnostic method from different AEZs in Pakistan. These findings will aid in establishing the distribution patterns and the control of tick-borne pathogens of bovines in Pakistan.