Effective Methods of Estimation of Pathogen Prevalence in Pooled Ticks

The Release of Non-Native Gamebirds Is Associated With Amplified Zoonotic Disease Risk

Spillback-where non-native species increase native pathogen prevalence-is potentially an important mechanism by which non-natives contribute to zoonotic disease emergence. However, spillback has not yet been directly demonstrated because it is difficult to disentangle from confounding factors which correlate with non-native species abundance and native pathogen prevalence. Here, we capitalise on replicated, quasi-experimental releases of non-native pheasants (Phasianus colchicus) to compare vector abundance and native pathogen prevalence between sites with similar local conditions but different non-native densities. Prevalence of Borrelia spp. (the causative agent of Lyme disease) in questing ticks was almost 2.5x higher in woods where pheasants are released compared to control woods, with a particularly strong effect on Borrelia garinii, a bird specialist genospecies. Furthermore, adult (but not nymphal) ticks tended to be more abundant at pheasant-release woods. This work provides evidence that non-native species can impact zoonotic pathogen prevalence via spillback in ecologically relevant contexts.

Molecular detection and characterization of Rickettsia felis, R. asembonensis, and Yersinia pestis from peri-domestic fleas in Uganda

Background: Fleas transmit a variety of zoonotic agents whose epidemiology and public health risk remains poorly understood in sub-Saharan Africa, including Uganda particularly outside plague-endemic areas. Common flea-borne zoonotic agents include Rickettsia felis and Yersinia pestis.. Objectives: The study aimed at detecting and characterising flea-borne pathogens in peridomestic environments in Uganda. Methods: We collected fleas from domestic animals, chickens, rodents, and homestead environments; pooled them by species, collection time, and host species. A total of 172 pools were analyzed for Y. pestis Pla gene. Further, 62 pools were tested for Rickettsia species gltA, ompA, and htrA genes by PCR and Sanger sequencing. Results: Five flea species were identified: C. canis, C. felis, Echidnophaga gallinacea, Pulex irritans, and X. cheopis. Genus, Ctenocephalides, accounted for 84.8% of fleas collected, mostly found on dogs and goats. The flea species were found across all districts, year-round, with higher numbers collected in dry seasons than rainy seasons. Rattus rattus constituted 74% of rodents captured from human dwellings and was the only rodent species with fleas, where X. cheopis was the predominant species. All 172 pools were negative for Y. pestis. Rickettsia spp. was detected in 29/62 (46.8%) pools by the target genes. Of 25 htrA amplicons sequenced, 4% were identified as R. felis from C. canis, 92% were R. asembonensis from multiple flea species, and 4% were identified as Candidatus Rickettsia senegalensis. Conclusion:The survey identified high pool detection rate of Rickettsia spp. in fleas,suggestingrisk of human exposure and infection. This was the first report of Rickettsia spp. in E. gallinacea and detection of Candidatus R. senegalensis in Uganda.

Assessing zoonotic risk in a fenced natural park in northwestern Italy: integrating camera traps for a vector-host approach to investigate tick-borne pathogens

Tick-borne diseases are among the major widespread emerging zoonotic diseases, and their circulation in the environment is influenced by a broad range of abiotic and biotic factors, including the abundance of vectors and vertebrate hosts. In this study, we estimated the prevalence of tick-borne pathogens and the impact of wildlife head count on their circulation in a lowland natural area in northwestern Italy. We collected ticks and camera trap pictures from 14 sampling points every 2 weeks for 1 year and identified pathogens through molecular analyses: Babesia capreoli, B. microti-like, Borrelia burgdorferi sensu lato (s.l.), Rickettsia of the spotted fever group (SFG), Theileria capreoli, and Anaplasma phagocytophilum. We modeled the presence of B. capreoli, B. microti-like, B. burgdorferi s.l., and SFG Rickettsia on head counts of wild ungulates and mesocarnivores. We tested a global model including all collected ticks, as well as a model focusing solely on Ixodes ricinus nymphs, the species, and the developmental stage most associated with zoonotic infection risk. The highest prevalence was obtained for B. microti-like (13%) and SFG Rickettsia (11%), and, for most pathogens, no differences were detected among tick species and their developmental stages. Mesocarnivores showed an additive effect on B. microti-like and B. burgdorferi s.l., while wild ungulates, non-competent for transmission of our target pathogens, showed a dilutive effect. These findings confirm the circulation of relevant tick-borne pathogens in the study area and show the use of camera trap data in predicting tick-borne pathogens' risk by targeting host species which may have an indirect impact and are more easily addressed by monitoring and control strategies.

Vector-borne pathogens in dogs and in Rhipicephalus sanguineus sensu stricto ticks in Morocco

Canine vector-borne diseases (CVBDs) are of major concern in veterinary medicine worldwide. Amongst the arthropods transmitting CVBD-causing pathogens, the brown dog tick (Rhipicephalus sanguineus sensu lato) is an important vector of agents, such as Babesia vogeli, Cercopithifilaria spp., Ehrlichia canis, Hepatozoon canis, and Anaplasma platys. While data on CVBDs transmitted by Rh. sanguineus s.l. are limited in Morocco, Leishmania spp., transmitted by phlebotomine sand flies, are known to be endemic in several regions of the country. In this study, we investigated the occurrence of tick-borne pathogens (TBPs) (i.e., Anaplasma spp., Babesia spp., Ehrlichia spp., Hepatozoon spp., Rickettsia spp.), Leishmania spp. and filarioids in shelter dogs and their ticks in central Morocco. Blood samples were collected from 144 dogs, and 5,363 ticks were removed from 314 dogs of the same population. DNA samples extracted from blood and from 276 ticks (divided into 55 pools) were screened for selected pathogens by PCR and DNA sequencing. Ticks were morphologically identified as Rh. sanguineus s.l., and molecular analysis of 10 representative specimens confirmed them as Rh. sanguineus s.s. Out of 144 dogs tested, 78 (54.1 %) scored positive for at least one pathogen, with 15 (10.4 %) being co-infected. H. canis was the most prevalent pathogen (38.2 %, 55/144), followed by L. infantum (15.3 %; 22/144), A. platys (5.6 %; 8/144), B. vogeli and E. canis (2.8 %; 4/144). Tick DNA pools scored positive for H. canis (36.4 %; n = 20/55). All dogs tested negative for filarioids and Rickettsia spp. Data herein reported demonstrate a high overall prevalence of CVBD-causing pathogens in dogs from central Morocco, with the unprecedented report of H. canis in dogs and ticks in this country.

Borrelia burgdorferi sensu lato prevalence in Ixodes scapularis from Canada: A thirty-year summary and meta-analysis (1990-2020)

Borrelia burgdorferi sensu lato (Bb) are a complex of bacteria genospecies that can cause Lyme disease (LD) in humans after the bite of an infected Ixodes spp. vector tick. In Canada, incidence of LD is increasing in part due to the rapid geographic expansion of Ixodes scapularis across the southcentral and eastern provinces. To better understand temporal and spatial (provincial) prevalence of Bb infection of I. scapularis and how tick surveillance is utilized in Canada to assess LD risk, a literature review was conducted. Tick surveillance studies published between January 1975 to November 2023, that measured the prevalence of Bb in I. scapularis via "passive surveillance" from the public citizenry or "active surveillance" by drag or flag sampling of host-seeking ticks in Canada were included for review. Meta-analyses were conducted via random effects modeling. Forty-seven articles, yielding 26 passive and 28 active surveillance studies, met inclusion criteria. Mean durations of collection for I. scapularis were 2.1 years in active surveillance studies (1999-2020) and 5.5 years by passive surveillance studies (1990-2020). Collectively, data were extracted on 99,528 I. scapularis nymphs and adults collected between 1990-2020 across nine provinces, including Newfoundland & Labrador (33 ticks) and Alberta (208 ticks). More studies were conducted in Ontario (36) than any other province. Across nine provinces, the prevalence of Bb infection in I. scapularis collected by passive surveillance was 14.6% with the highest prevalence in Nova Scotia at 20.5% (minimum studies >1). Among host-seeking I. scapularis collected via active surveillance, Bb infection prevalence was 10.5% in nymphs, 31.9% in adults, and 23.8% across both life stages. Host-seeking I. scapularis nymphs and adults from Ontario had the highest Bb prevalence at 13.6% and 34.8%, respectively. Between 2007-2019, Bb infection prevalence in host-seeking I. scapularis was positively associated over time (p<0.001) which is concurrent with a ∼25-fold increase in the number of annually reported LD cases in Canada over the same period. The prevalence of Bb-infection in I. scapularis has rapidly increased over three decades as reported by tick surveillance studies in Canada which coincides with increasing human incidence for LD. The wide-ranging distribution and variable prevalence of Bb-infected I. scapularis ticks across provinces demonstrates the growing need for long-term standardized tick surveillance to monitor the changing trends in I. scapularis populations and best define LD risk areas in Canada.

Investigation of Tick-Borne Pathogens in Ixodes Ticks from Bosnia and Herzegovina

Limited information is available regarding the presence of tick-borne pathogens and their distribution within Ixodes species in Bosnia and Herzegovina. This study aimed to identify Rickettsia spp., Babesia spp., Anaplasma phagocytophilum, and Borrelia burgdorferi sensu lato (s.l.) in Ixodes ticks collected from domestic and wild animals and vegetation in different regions across Bosnia and Herzegovina. A total of 7438 adult ticks, including 4526 Ixodes ricinus, Ixodes canisuga, and Ixodes hexagonus, were collected. Real-time PCR screening of 450 pooled I. ricinus samples revealed a 22.1% infection rate with at least one pathogen. Rickettsia spp. (6.3%) were found in ticks from dogs, cats, and goats, Babesia spp. (3.1%) in ticks from dogs and cattle, A. phagocytophilum (8.8%) in ticks from dogs, goats, and cattle, and B. burgdorferi s.l. (3.4%) in ticks from dogs and cats. Mixed infections with B. burgdorferi s.l. and A. phagocytophilum, as well as B. burgdorferi s.l. and Rickettsia spp., were found in two pools of I. ricinus from dogs and cats, respectively. Additionally, co-infection with Rickettsia spp. and A. phagocytophilum was confirmed in three tick pools from dogs and goats. Each tick from these pooled samples was individually retested to confirm the presence of pathogens. In the examined pooled samples of I. canisuga (1) and I. hexagonus (6), none of the tested pathogens were detected. Our findings represent the first detection of Rickettsia spp., Babesia spp., A. phagocytophilum, and B. burgdorferi s.l. in I. ricinus collected from domestic animals and vegetation in Bosnia and Herzegovina. Considering the established infection rates, the detection of tick-borne pathogens in adult ticks collected from domestic animals and vegetation enriches the current knowledge of the presence of tick-borne pathogens at the local, regional, national, and broader levels.

Molecular Identification of Spotted Fever Group Rickettsiae in Ticks in the Republic of Korea

The Rickettsia species transmitted by ticks are mostly classified within the spotted fever group rickettsiae (SFGR), which causes tick-borne rickettsiosis. Although efforts have been made to investigate their prevalence in the Republic of Korea (ROK), research has been limited to certain areas. Furthermore, the pooling method for ticks does not fully reflect the exact infection rate. Therefore, we aimed to perform molecular identification of SFGR in ticks to elucidate the current prevalence of tick-borne rickettsiosis in the ROK. The SFGR of ticks was identified using polymerase chain reaction targeting the 17 kDa antigen, ompA, and gltA, followed by sequencing for species identification and phylogenetic analysis. In total, 302 ticks belonging to four species (Haemaphysalis flava, H. longicornis, Ixodes nipponensis, and Amblyomma testudinarium) were collected between April and November 2022. The overall SFGR infection rate was 26.8% (81/302 patients). Both adult and nymphal ticks and the SFGR infection rate increased during April-May, reaching their peaks in June, followed by a marked decline in August and July, respectively. Phylogenetic analysis revealed three species (R. monacensis, R. heilongjiangensis, and Candidatus R. jingxinensis) of SFGR. Thus, our results emphasize the importance of tick surveys for the prevention and management of tick-borne rickettsiosis.

Tick abundance and infection with three zoonotic bacteria are heterogeneous in a Belgian peri-urban forest

Ixodes ricinus is a vector of several pathogens of public health interest. While forests are the primary habitat for I. ricinus, its abundance and infection prevalence are expected to vary within forest stands. This study assesses the spatio-temporal variations in tick abundance and infection prevalence with three pathogens in and around a peri-urban forest where human exposure is high. Ticks were sampled multiple times in 2016 and 2018 in multiple locations with a diversity of undergrowth, using the consecutive drags method. Three zoonotic pathogens were screened for, Borrelia burgdorferi s.l., Coxiella burnetii, and Francisella tularensis. The influence of season, type of site and micro-environmental factors on tick abundance were assessed with negative binomial generalized linear mixed-effects models. We collected 1642 nymphs and 181 adult ticks. Ticks were most abundant in the spring, in warmer temperatures, and where undergrowth was higher. Sites with vegetation unaffected by human presence had higher abundance of ticks. Forest undergrowth type and height were significant predictors of the level of tick abundance in a forest. The consecutive drags method is expected to provide more precise estimates of tick abundance, presumably through more varied contacts with foliage. Borrelia burgdorferi s.l. prevalence was estimated from pooled ticks at 5.33%, C. burnetii was detected in six pools and F. tularensis was not detected. Borrelia afzelii was the dominant B. burgdorferi genospecies. Tick abundance and B. burgdorferi s.l. infection prevalence were lower than other estimates in Belgian forests.

Distribution and pathogen prevalence of field-collected ticks from south-western Korea: a study from 2019 to 2022

Hard ticks are known vectors of various pathogens, including the severe fever with thrombocytopenia syndrome virus, Rickettsia spp., Coxiella burnetii, Borrelia spp., Anaplasma phagocytophilum, and Ehrlichia spp. This study aims to investigate the distribution and prevalence of tick-borne pathogens in southwestern Korea from 2019 to 2022. A total of 13,280 ticks were collected during the study period, with H. longicornis accounting for 86.1% of the collected ticks. H. flava, I. nipponensis and A. testudinarium comprised 9.4%, 3.6%, and 0.8% of the ticks, respectively. Among 983 pools tested, Rickettsia spp. (216 pools, 1.6% MIR) were the most prevalent pathogens across all tick species, with R. japonica and R. monacensis frequently detected in I. nipponensis and Haemaphysalis spp., respectively. Borrelia spp. (28 pools, 0.2% MIR) were predominantly detected in I. nipponensis (27 pools, 13.8% MIR, P < 0.001). Co-infections, mainly involving Rickettsia monacensis and Borrelia afzelii, were detected in I. nipponensis. Notably, this study identified R. monacensis for the first time in A. testudinarium in South Korea. These findings offer valuable insights into the tick population and associated pathogens in the region, underscoring the importance of tick-borne disease surveillance and prevention measures.

Zalati CS, Hamdan RH, Samoh A, Loong SK. Molecular prevalence of Bartonella spp. in bat flies in east coast Malaysia

Bats are a significant reservoir for numerous pathogens, including Bartonella spp. It is one of the emerging zoonotic bacterial diseases that can be transmitted to humans and may cause various unspecific clinical manifestations. Thus, bartonellosis is rarely diagnosed and is regarded as a neglected vector-borne disease (VBD). Bat flies have been hypothesised to be a vector in the transmission of pathogens among bats. They are host-specific, which reduces the likelihood of pathogen transmission across bat species; however, they are likely to maintain high pathogen loads within their host species. To explore the presence of Bartonella spp. in bat flies from Peninsular Malaysia; bat fly samples collected from various sites at the east coast states were subjected to molecular detection for Bartonella spp. It was discovered that 38.7 % of bats from Terengganu and Kelantan were infested with bat flies; however, no bat fly was found in bats collected from Pahang. The collected bat flies belonged to the families Nycteribiidae (79.6 %) and Streblidae (20.4 %). The collected bat flies were pooled according to the locations and species into 39 pools. Out of these 39 pools, 66.7 % (n = 26) were positive for Bartonella spp. by PCR. Sequence analyses of five randomly selected PCR-positive pools revealed that pools from Kelantan (n = 3) have the closest sequence identities (99 %) to Bartonella spp. strain Lisso-Nig-922 from Nigeria. However, the other pools from Terengganu (n = 2) were closely related to Bartonella spp. strain KP277 from Thailand and Bartonella spp. strain Rhin-3 from the Republic of Georgia with 99 % and 100 % sequence identity, respectively. This suggests that the Bartonella spp. found in Malaysian bat flies are genetically diverse and can potentially serve as reservoirs for pathogenic Bartonella spp.

Biting Back: Advances in Fighting Ticks and Understanding Tick-Borne Pathogens

Ticks are blood-feeding arthropods and obligate ectoparasites of virtually all animal species (except fish) and humans [...].