Current research in parasitology & vector-borne diseases最新文献

Birds are long-known as important disseminators of ixodid ticks, in which context mostly their latitudinal, south-to-north migration is considered. However, several bird species that occur in the eastern part of the northern Palaearctic are known to migrate westward. In this study, a female tick collected from the sedge warbler, Acrocephalus schoenobaenus, in Lithuania was identified morphologically and analyzed with molecular-phylogenetic methods. In addition, literature data were reviewed on ixodid tick species known to be associated with birds that have recorded east-to-west migratory route in the Palaearctic. The tick collected from A. schoenobaenus was morphologically identified as Ixodes apronophorus. Two mitochondrial genetic markers for this specimen showed 100% identity with a conspecific tick reported previously in Western Siberia, Russia. Based on literature data, as many as 82 bird species from 11 orders were found to have records of ringing in the easternmost part of the northern Palaearctic and recaptures in Europe. Of these bird species, 31 ixodid tick species were reported in the Euro-Siberian region. Nearly all passeriform bird species with east-to-west migration were reported to carry ticks, whereas no reports of tick infestation were documented from the majority of wetland-associated bird species, mostly from the orders Anseriformes and Charadriiformes. The first European sequences of bona fide I. apronophorus revealed genetic connectedness with conspecific ticks reported from Siberia. Since the principal hosts of this tick species are rodents which do not migrate large distances, the most likely explanation for genetic similarity in this direction is dispersal of this tick species via migratory birds. Given the high number of tick species that are known to associate with bird species migrating in westward direction, this appears to be an important means of the gene flow between geographically distant tick populations in the northern Palaearctic.

Tick-borne diseases (TBD) represent an important challenge for human and veterinary medicine. In Slovakia, studies on the epidemiology of tick-borne pathogens (TBP) regarding reservoir hosts have focused on small mammals and to a lesser extent on birds or lizards, while knowledge of the role of the remaining vertebrate groups is limited. Generally, wild ungulates, hedgehogs, small- and medium-sized carnivores, or squirrels are important feeding hosts for ticks and serve as reservoirs for TBP. Importantly, because they carry infected ticks and/or are serologically positive, they can be used as sentinels to monitor the presence of ticks and TBP in the environment. With their increasing occurrence in urban and suburban habitats, wild ungulates, hedgehogs or foxes are becoming an important component in the developmental cycle of Ixodes ricinus and of TBP such as Anaplasma phagocytophilum or Babesia spp. On the other hand, it has been postulated that cervids may act as dilution hosts for Borrelia burgdorferi (sensu lato) and tick-borne encephalitis virus. In southwestern Slovakia, a high prevalence of infection with Theileria spp. (100%) was observed in some cervid populations, while A. phagocytophilum (prevalence of c.50%) was detected in cervids and wild boars. The following pathogens were detected in ticks feeding on free-ranging ungulates, birds, and hedgehogs: A. phagocytophilum, Rickettsia spp., Coxiella burnetii, Neoehrlichia mikurensis, B. burgdorferi (s.l.), and Babesia spp. The growing understanding of the role of wildlife as pathogen reservoirs and carriers of pathogen-infected ticks offers valuable insights into the epidemiology of TBP, providing a foundation for reducing the risk of TBD.

Ticks are important ectoparasites of domestic animals, wild animals and humans. They spread a variety of infective agents such as protozoans, viruses, and bacteria. Cattle reared by smallholder farmers are susceptible to ticks and tick-borne pathogens due to the type of production system practiced by the farmers. Hence, this review was focused on the occurrence of ticks and tick-borne pathogens in cattle reared by smallholder farmers in South Africa. The systematic search produced a total of 13,408 articles from four databases, and after screening processes, the review utilized 23 articles published between 1983 and 2023. A total of 26 tick species belonging to seven genera were identified in the reviewed articles, with Rhipicephalus (Boophilus) decoloratus and Rhipicephalus evertsi evertsi being the most frequently reported tick species in South Africa followed by Amblyomma hebreum, Rhipicephalus appendiculatus, Hyalomma marginatum rufipes, Rhipicephalus microplus, Rhipicephalus follis, Rhipicephalus gertrudae and Hyalomma truncatum. The most frequently reported tick-borne pathogens across the provinces included Babesia bigemina, Babesia bovis, and Anaplasma marginale, with Eastern Cape Province accounting for most of the records followed by KwaZulu-Natal and Mpumalanga Provinces. The findings of this review confirm that cattle reared by smallholder farmers harbour various ticks and tick-borne pathogens of veterinary, public health and economic importance, and regular monitoring of tick infestations in South Africa is recommended to avoid disease outbreaks.

Feline hepatozoonosis is a vector-borne disease caused by different species of the genus Hepatozoon, i.e. Hepatozoon felis, Hepatozoon silvestris and Hepatozoon canis. Knowledge on the biology, epidemiology and taxonomy of Hepatozoon spp. is still limited, despite the fact that the number of documented Hepatozoon spp. infections in domestic cats increased in recent years in different countries. This study was carried out to evaluate the prevalence and the genetic profile of Hepatozoon spp. in cats living on the island of Skopelos, Greece. Individual blood samples were collected from 54 owned cats and were subjected to Giemsa-stained blood smear examination to investigate the presence of Hepatozoon spp. gamonts and to a specific PCR protocol targeting the 18S rRNA gene of Hepatozoon. A total of 45 cats (83.3%) were found infected by Hepatozoon spp. by at least one of the methods applied. In particular, 43 (79.6%) of the cats were PCR-positive, and in 6 (11.1%) cats gamonts of Hepatozoon spp. were found in the blood smears. A total of 26 H. felis sequences were obtained and the presence of three undescribed single nucleotide polymorphisms were detected. The present results indicate that H. felis species complex may be hyperendemic in isolated/confined areas. In such contexts, geographical isolation may favor the origin of new genotypes or haplotypes or even new species.

Understanding the dynamics of malaria vectors and their interactions with environmental factors is crucial for effective malaria control. This study investigated the abundance, species composition, seasonal variations, and malaria infection status of female mosquitoes in malaria transmission and non-transmission areas in Western Thailand. Additionally, the susceptibility of malaria vectors to pyrethroid insecticides was assessed. Entomological field surveys were conducted during the hot, wet, and cold seasons in both malaria transmission areas (TA) and non-transmission areas (NTA). The abundance and species composition of malaria vectors were compared between TA and NTA. The availability of larval habitats and the impact of seasonality on vector abundance were analyzed. Infection with Plasmodium spp. in primary malaria vectors was determined using molecular techniques. Furthermore, the susceptibility of malaria vectors to pyrethroids was evaluated using the World Health Organization (WHO) susceptibility test. A total of 9799 female mosquitoes belonging to 54 species and 11 genera were collected using various trapping methods. The number of malaria vectors was significantly higher in TA compared to NTA (P < 0.001). Anopheles minimus and An. aconitus were the predominant species in TA, comprising over 50% and 30% of the total mosquitoes collected, respectively. Seasonality had a significant effect on the availability of larval habitats in both areas (P < 0.05) but did not impact the abundance of adult vectors (P > 0.05). The primary malaria vectors tested were not infected with Plasmodium spp. The WHO susceptibility test revealed high susceptibility of malaria vectors to pyrethroids, with mortality rates of 99–100% at discriminating concentrations. The higher abundance of malaria vectors in the transmission areas underscores the need for targeted control measures in these regions. The susceptibility of malaria vectors to pyrethroids suggests the continued effectiveness of this class of insecticides for vector control interventions. Other factors influencing malaria transmission risk in the study areas are discussed. These findings contribute to our understanding of malaria vectors and can inform evidence-based strategies for malaria control and elimination efforts in Western Thailand.

A crucial factor to predict the persistence and spread of infections in natural systems is the capacity of reservoir hosts to maintain the infection and transmit it to others. This is known to greatly vary within and between species and through time, although the latter part of the variation is often less well understood in the wild. Borrelia garinii is one of the causal agents of Lyme disease in humans and is transmitted among avian hosts by the hard tick Ixodes ricinus. Great tits are known to be a reservoir in Europe for B. garinii. For tick-borne pathogens like B. garinii, infectiousness or host-to-vector transmission can be measured using xenodiagnosis where pathogen-free vectors are fed on a host, and the blood-fed vectors are subsequently tested for the pathogen. Here we describe and evaluate a methodology to quantify infectiousness for tick-borne pathogens in individual wild great tits (Parus major), involving captures and recaptures of targeted individuals. The methodology can potentially be applied to other species where recapturing is sufficiently guaranteed. We successfully recaptured most of the infested great tits two to three days after initial infestation (i.e. just before ticks have fully fed) with sufficient numbers of I. ricinus larval ticks, which were subsequently screened for B. garinii using a newly developed B. garinii-specific real-time PCR assay. Higher larval tick numbers were recovered from birds during the breeding seasons than during the winter months. Our novel B. garinii-qPCR performed well, and greatly reduced the amount of Sanger sequencing needed. Preliminary results suggest both seasonal and individual variation in infectiousness; heterogeneity that needs to be unravelled to further understand the contribution of resident birds to the epidemiology of B. garinii.