On the possible role of ticks in the eco-epidemiology of Coxiella burnetii in a Mediterranean ecosystem

Dynamics of Crimean-Congo hemorrhagic fever virus in two wild ungulate hosts during a disease-induced population collapse

Identifying the role that host species play in pathogen transmission and maintenance is crucial for disease control, but it is a difficult task, in particular for vector-borne and multi-host pathogens, and especially when wildlife species are involved. This is the case for a Crimean-Congo hemorrhagic fever virus (CCHFV) hotspot in north-eastern Spain, where Iberian ibex (Capra pyrenaica) and wild boar (Sus scrofa) are involved, but their roles in disease transmission are unclear. In this context, we studied the dynamics of CCHFV transmission in these two species during the collapse of an Iberian ibex population due to a sarcoptic mange outbreak. We carried out a repeated cross-sectional study measuring the trends of CCHFV seroprevalence in Iberian ibex and wild boar and their abundances. In addition, we identified the tick species present in this area on the vegetation and on wild boars, and evaluated relevant meteorological factors. Results show that while the trends in CCHFV seroprevalence in Iberian Ibex and density of wild boars remained constant (p = 1.0 and p = 0.8, respectively), both the trends in Iberian ibex census and CCHFV seroprevalence in wild boars decreased significantly (p = 0.003 and p = 0.0001, respectively), and were correlated (Spearman's rank, 0.02 < p-adjusted<0.05). The correlation between the patterns of reduction of Iberian ibex abundance and the decrease of seroprevalence in wild boars suggests some sort of shared transmission cycle between the two species. Data from tick species in the area suggest a possible role of Rhipicephalus bursa in CCHFV transmission. The dynamics of CCHFV were unlikely caused by changes in meteorological variables such as temperature or water vapor pressure deficit. Further studies will be needed to confirm these hypotheses.

Molecular investigation of Coxiella burnetii and Francisella tularensis infection in ticks in northern, western, and northwestern Iran

Tularemia and Q fever are endemic diseases in Iran; however, little information is available on the prevalence of the causative agents, Coxiella burnetii and Francisella tularensis, in Iranian ticks. This study investigated C. burnetii and F. tularensis among hard ticks in this country. We collected ticks from livestock and other mammals in Guilan, Mazandaran, Golestan (northern Iran), Kurdistan (western Iran), and West Azerbaijan (northwestern Iran) provinces. Genomic DNA from collected ticks was extracted and screened for C. burnetii and F. tularensis using Real-time PCR. A total of 4,197 ticks (belonging to 12 different species) were collected, and Ixodes ricinus (46.4%), Rhipicephalus turanicus (25%), and Rhipicephalus sanguineus sensu lato (19.1%) were the most collected species. Of 708 pooled tick samples, 11.3% and 7.20% were positive for C. burnetii and F. tularensis, respectively. The genus of Rhipicephalus had the highest (18.3%) C. burnetii infection among the collected tick pools (P<0.001). Furthermore, the most positive pools for F. tularensis belonged to Haemaphysalis spp. (44.4%). Kurdistan had the most significant percentage of C. burnetii-infected ticks (92.5%), and there was a meaningful relationship between the provinces and the infection (P< 0.001). The ticks from Golestan exhibited the highest F. tularensis infection rate (10. 9%), and the infection showed no significant relationship with the provinces (P = 0.19). Ticks collected from grasslands had a higher Coxiella burnetii infection rate than those collected from animals (39.4% vs. 7.9%; p<0.01). However, ticks collected from animal surfaces had a slightly higher rate of Francisella tularensis infection than those collected from grasslands (7.6% vs. 3.9%; p = 0.24). Here, we demonstrated the presence of both pathogens in the north (Guilan, Mazandaran, and Golestan provinces), the west (Kurdistan province), and the northwest (West Azerbaijan province) of Iran. The public health system should pay particular attention to tick bites in veterinary medicine and humans.

Diseases of Iberian ibex (Capra pyrenaica)

Iberian ibex (Capra pyrenaica) is an ecologically and economically relevant medium-sized emblematic mountain ungulate. Diseases participate in the population dynamics of the species as a regulating agent, but can also threaten the conservation and viability of vulnerable population units. Moreover, Iberian ibex can also be a carrier or even a reservoir of pathogens shared with domestic animals and/or humans, being therefore a concern for livestock and public health. The objective of this review is to compile the currently available knowledge on (1) diseases of Iberian ibex, presented according to their relevance on the health and demography of free-ranging populations; (2) diseases subjected to heath surveillance plans; (3) other diseases reported in the species; and (4) diseases with particular relevance in captive Iberian ibex populations. The systematic review of all the information on diseases affecting the species unveils unpublished reports, scientific communications in meetings, and scientific articles, allowing the first comprehensive compilation of Iberian ibex diseases. This review identifies the gaps in knowledge regarding pathogenesis, immune response, diagnostic methods, treatment, and management of diseases in Iberian ibex, providing a base for future research. Moreover, this challenges wildlife and livestock disease and wildlife population managers to assess the priorities and policies currently implemented in Iberian ibex health surveillance and monitoring and disease management.

The relevance of the wild reservoir in zoonotic multi-host pathogens: The links between Iberian wild mammals and Coxiella burnetii

Q fever is a worldwide zoonosis caused by an obligate intracellular bacterium, Coxiella burnetii, with only anecdotal reports of human-to-human transmission. The cause of human Q fever infections is the circulation of C. burnetii in animal reservoirs. Infected livestock, particularly goats and sheep, may cause Q fever outbreaks in humans. However, wildlife is the origin of several human Q fever cases. Human impacts on habitats, biodiversity and climate are responsible for changes in the patterns of interaction between domestic animals, wildlife and humans, allowing wild animals to play an increasingly relevant role as Q fever reservoirs. In the Iberian Peninsula, human impacts on the environment combined with a high biodiversity, which could maintain high transmission rates of this multi-host pathogen, make wild reservoirs an important piece in Q fever epidemiology. In this study, we review the reporting of C. burnetii infections and exposure in Iberian wild mammals and analyse the link between the diversity of wild mammals and the frequency of C. burnetii notifications in wildlife. For it, the number of wild mammal species per UTM 10 × 10-km grid in mainland Spain and Portugal was estimated as a potential predictor of C. burnetii transmission. The results of non-linear regression analysis showed a quadratic relationship between the number of wild mammal species per grid and the presence of C. burnetii cases reported in the literature both by serology (R²  = 0.86) and polymerase chain reaction (R²  = 0.83). Increasing wild mammal diversity was linked to increasing C. burnetii transmission until an intermediate level when the relationship was inverted. Thus, at high levels of wild mammal diversity, the risk of C. burnetii transmission was lower. These observations show a role of wild mammal biodiversity in C. burnetii ecology that needs to be further explored to better prevent the negative impact of Q fever in livestock and human health in Iberia.

First serological evidence of Q fever in large ruminants and its associated risk factors in Punjab, Pakistan

Coxiellosis, also known as Q fever, is a zoonotic disease caused by Coxiella burnetii, a gram-negative bacterium that exerts a significant deleterious impact on the productive and reproductive capabilities of livestock, severely effecting the economics of this sector. In this study, 448 sera samples from cattle (n = 224) and buffalo (n = 224) were collected from 112 farms in Pakistan and examined for antibodies against C. burnetii using an indirect ELISA. Ticks were also collected from these animals. Serological analysis revealed a 23.66% and 27.23% seroprevalence of Q fever in cattle and buffalo, respectively. Odds ratio (OR) analysis of the factors associated with C. burnetii seropositivity was performed, and a multivariable logistic model identified five main variables associated with the seropositivity for coxiellosis. These were: (i) the absence of acaricide use (OR 5.61; 95% CI 2.97-10.94); (ii) the presence of ticks (OR 3.23; 95% CI 1.87-5.69); (iii) the abortion history during the preceding year on the farm (OR 14.96; 95% CI 8.09-29.34); (iv) the presence of sheep and goats (OR 2.47; 95% CI 1.20-5.35); and (v) the absence of a separate parturition area (OR 3.17; 95% CI 1.76-5.86). This study provides new insights into the seroprevalence of Q fever in large ruminants across seven studied districts of Punjab, Pakistan, also providing baseline data to inform improved herd management and on-farm practices for the prevention and control of Q fever in large ruminants in the region. Results of this work suggest that further molecular investigation of coxiellosis is warranted to provide a more thorough evaluation of C. burnetii epidemiology in Pakistan.

Molecular detection and genetic characterization of Coxiella-like endosymbionts in dogs and ticks infesting dogs in Northeast India

An epidemiological study was performed to determine the role of dogs and ticks infesting dogs in the transmission of Q fever in humans and animals from April 2019 to March 2020 in the northeastern hill states of India. In total, 245 pet and stray dogs irrespective of age or sex were sampled, without specific inclusion or exclusion criteria. In total, 478 ticks belonging to three species were detected, namely Rhipicephalus sanguineus, Rhipicephalus (Boophilus) microplus and Hyalomma anatolicum anatolicum. The DNA extracted from blood and tick samples was assayed for molecular characterization of Coxiella burnetii targeting the 16S rRNA and superoxide dismutase (SOD) genes. Amplified PCR products were purified, cloned and custom sequenced. PCR assay showed 3.3% (8/245) of the dogs were positive for Coxiella-like bacteria. Coxiella-like bacterial DNA was detected in adult fully engorged females of R. sanguineus (7.7%, 13/168), R. (B.) microplus (3.3%, 4/123) and H. anatolicum (1.9%, 1/54). Coxiella-like bacterial DNA lacked in adult male or nymphal stage. The infection rate did not vary significantly between seasons, nor according to sex or age of the host. Six nucleotide sequences of 16S rRNA and SOD genes are discussed.

Seasonality of Coxiella burnetii among Wild Rabbits (Oryctolagus cuniculus) and the Hyalomma lusitanicum (Acari: Ixodidae) in a Meso-Mediterranean Ecosystem

(1) Background: Q fever is a worldwide zoonosis caused by Coxiella burnetii that have cases reported in humans and animals almost everywhere. The aim of this study was to describe the seasonality of Coxiella burnetii in the wild rabbit (Oryctolagus cuniculus) and the tick Hyalomma lusitanicum in a meso-Mediterranean ecosystem. (2) Methods: two populations of wild rabbits that differ in whether or not they share habitat with ungulates, mainly red deer (Cervus elaphus) were sampled for a year to collect ticks, blood and vaginal or anal swabs. Presence of C. burnetii DNA in swabs and the tick H. lusitanicum was determined by PCR and serum antibodies by ELISA. (3) Results: C. burnetii DNA was detected in 47.2% of 583 rabbits, in 65.5% of sera, and in more than half of the H. lusitanicum. There were small variations according to sex and age of the rabbits but significant according to the habitat (4) Conclusions: The results indicate that C. burnetii circulates freely between wild rabbits and H. lusitanicum and the sylvatic cycle in meso-Mediterranean environments relies in the presence of wild rabbits and H. lusitanicum above all if sharing habitat with red deer.

Recent Advances on the Innate Immune Response to Coxiella burnetii

Coxiella burnetii is an obligate intracellular Gram-negative bacterium and the causative agent of a worldwide zoonosis known as Q fever. The pathogen invades monocytes and macrophages, replicating within acidic phagolysosomes and evading host defenses through different immune evasion strategies that are mainly associated with the structure of its lipopolysaccharide. The main transmission routes are aerosols and ingestion of fomites from infected animals. The innate immune system provides the first host defense against the microorganism, and it is crucial to direct the infection towards a self-limiting respiratory disease or the chronic form. This review reports the advances in understanding the mechanisms of innate immunity acting during C. burnetii infection and the strategies that pathogen put in place to infect the host cells and to modify the expression of specific host cell genes in order to subvert cellular processes. The mechanisms through which different cell types with different genetic backgrounds are differently susceptible to C. burnetii intracellular growth are discussed. The subsets of cytokines induced following C. burnetii infection as well as the pathogen influence on an inflammasome-mediated response are also described. Finally, we discuss the use of animal experimental systems for studying the innate immune response against C. burnetii and discovering novel methods for prevention and treatment of disease in humans and livestock.

Ticks on wild boar in the metropolitan area of Barcelona (Spain) are infected with spotted fever group rickettsiae

Tick-borne pathogens (TBPs) constitute an emerging public health concern favoured by multidimensional global changes. Amongst these, increase and spread of wild boar (Sus scrofa) populations are of special concern since this species can act as a reservoir of zoonotic pathogens and promote tick abundance. Thus, we aimed to make a first assessment of the risk by TBPs resulting from wild boar and ticks in the vicinity of a highly populated area. Between 2014 and 2016, we collected spleen samples and 2256 ticks from 261 wild boars (out of 438 inspected) in the metropolitan area of Barcelona (MAB; northeast Spain). We morphologically identified four tick species: Hyalomma lusitanicum (infestation prevalence: 33.6%), Dermacentor marginatus (26.9%), Rhipicephalus sanguineus sensu lato (18.9%) and R. bursa (0.2%). Ticks were pooled according to species and individual host. A total of 180 tick pools and 167 spleen samples were screened by real-time PCR and/or reverse line blot hybridization assay for Ehrlichia sp., Anaplasma sp., Babesia sp., Rickettsia sp., Borrelia burgdorferi sensu lato and Coxiella burnetii. Seventy-two out of the 180 tick pools were positive to Rickettsia spp. (minimum prevalence of 8.7%), including Rickettsia massiliae, R. slovaca and R. raoultii. We did not detect Rickettsia spp. in wild boar spleens nor other TBPs in ticks or wild boars. Since the ticks identified can bite humans, and the recorded spotted fever group (SFG) rickettsiae are zoonotic pathogens, there is a risk of SFG rickettsiae transmission for MAB inhabitants. Our results suggest a broader distribution of H. lusitanicum, competent vector for the Crimean-Congo haemorrhagic fever virus than previously known. Wild boar is not a Rickettsia spp. reservoir according to the spleen negative results. However, its abundance could favour tick life cycle and abundance, and its proximity to humans could promote the infection risk by Rickettsia spp.

The Prevalence of Coxiella burnetii in Hard Ticks in Europe and Their Role in Q Fever Transmission Revisited-A Systematic Review

The zoonosis Q fever is caused by the obligate intracellular bacterium Coxiella burnetii. Besides the main transmission route via inhalation of contaminated aerosols, ticks are discussed as vectors since the first isolation of the pathogen from a Dermacentor andersonii tick. The rare detection of C. burnetii in ticks and the difficult differentiation of C. burnetii from Coxiella-like endosymbionts (CLEs) are questioning the relevance of ticks in the epidemiology of Q fever. In this review, literature databases were systematically searched for recent prevalence studies concerning C. burnetii in ticks in Europe and experimental studies evaluating the vector competence of tick species. A total of 72 prevalence studies were included and evaluated regarding DNA detection methods and collection methods, country, and tested tick species. Specimens of more than 25 different tick species were collected in 23 European countries. Overall, an average prevalence of 4.8% was determined. However, in half of the studies, no Coxiella-DNA was detected. In Southern European countries, a significantly higher prevalence was observed, possibly related to the abundance of different tick species here, namely Hyalomma spp. and Rhipicephalus spp. In comparison, a similar proportion of studies used ticks sampled by flagging and dragging or tick collection from animals, under 30% of the total tick samples derived from the latter. There was no significant difference in the various target genes used for the molecular test. In most of the studies, no distinction was made between C. burnetii and CLEs. The application of specific detection methods and the confirmation of positive results are crucial to determine the role of ticks in Q fever transmission. Only two studies were available, which assessed the vector competence of ticks for C. burnetii in the last 20 years, demonstrating the need for further research.

Mitochondrial sequences of Rhipicephalus and Coxiella endosymbiont reveal evidence of lineages co-cladogenesis

Rhipicephalus ticks are competent vectors of several pathogens, such as Spotted Fever Group Rickettsiae (SFGR) and many Babesia species. Within this genus, different R. sanguineus s.l. lineages show an unequal vector competence and resistance regarding some pathogenic strains. Current literature supports that tick endosymbionts may play an essential role in the transmission ability of a vector. Indeed, the microbial community of Rhipicephalus seems to be dominated by Coxiella-like endosymbionts (CLE). Still, their co-evolutionary associations with the complicated phylogeny of Rhipicephalus lineages and their transmissible pathogens remain unclear. We performed a phylogenetic congruence analysis to address whether divergent R. sanguineus s.l. lineages had a different symbiont composition. For that, we applied a PCR based approach to screen part of the microbial community present in 279 Rhipicephalus ticks from the Iberian Peninsula and Africa. Our analyses detected several qPCR-positive signals for both SFGR and Babesia species, of which we suggest R. sanguineus-tropical lineage as a natural vector of Babesia vogeli and R. sanguineus-temperate lineage of SFGR. The acquisition of 190 CLE sequences allowed to evaluate co-phylogenetic associations between the tick and the symbiont. With this data, we observed a strong but incomplete co-cladogenesis between CLE strains and their Rhipicephalus tick lineages hosts.

Molecular Investigation of the Status of Ticks on Infected Cattle for Coxiella burnetii in India

PURPOSE

In Indian subcontinent, the epidemiological studies on the status of ticks in the transmission of Coxiella burnetii have not been explored comprehensively. The objective of the present study was to investigate the status of ticks for C. burnetii among coxiellosis positive cattle.

METHODS

The present study was carried out in three locations of the northern states of India. A total of 1648 tick samples were collected from the tick infested cattle (n = 146) that were tested positive for coxiellosis by indirect serum-ELISA assay and/or the trans-PCR assay. The tick samples were screened using the trans-PCR assay targeting species-specific IS1111 transposase gene of C. burnetii. The sequencing of PCR products was planned to differentiate C. burnetii and Coxiella-like bacteria (CLB).

RESULTS

The collected ticks were identified as Rhipicephalus microplus (n = 1049), Hyalomma anatolicum (n = 416), and Hyalomma spp. (n = 183). On molecular investigation, none of the collected tick samples were found to be positive for the IS1111 gene.

CONCLUSION

The findings of the present study ruled out the involvement of ticks in circulation of the pathogen within the cattle population that were screened. However, extensive epidemiological studies are needed to conclusively rule out or establish the role of ticks as a competent vector for C. burnetii transmission in cattle and other hosts.

Coxiella burnetii is widespread in ticks (Ixodidae) in the Xinjiang areas of China

Background

The gram-negative Coxiella burnetii bacterium is the pathogen that causes Q fever. The bacterium is transmitted to animals via ticks, and manure, air, dead infected animals, etc. and can cause infection in domestic animals, wild animals, and humans. Xinjiang, the provincial-level administrative region with the largest land area in China, has many endemic tick species. The infection rate of C. burnetii in ticks in Xinjiang border areas has not been studied in detail.

Results

For the current study, 1507 ticks were collected from livestock at 22 sampling sites in ten border regions of the Xinjiang Uygur Autonomous region from 2018 to 2019. C. burnetii was detected in 205/348 (58.91%) Dermacentor nuttalli; in 110/146 (75.34%) D. pavlovskyi; in 66/80 (82.50%) D. silvarum; in 15/32 (46.90%) D. niveus; in 28/132 (21.21%) Hyalomma rufipes; in 24/25 (96.00%) H. anatolicum; in 219/312 (70.19%) H. asiaticum; in 252/338 (74.56%) Rhipicephalus sanguineus; and in 54/92 (58.70%) Haemaphysalis punctata. Among these samples, C. burnetii was detected in D. pavlovskyi for the first time. The infection rate of Rhipicephalus was 74.56% (252/338), which was the highest among the four tick genera sampled, whereas the infection rate of H. anatolicum was 96% (24/25), which was the highest among the nine tick species sampled. A sequence analysis indicated that 63 16S rRNA sequences could be found in four newly established genotypes: MT498683.1 (n = 18), MT498684.1 (n = 33), MT498685.1 (n = 6), and MT498686.1 (n = 6).

Conclusions

This study indicates that MT498684.1 might represent the main C. burnetii genotype in the ticks in Xinjiang because it was detected in eight of the tick species studied. The high infection rate of C. burnetii detected in the ticks found in domestic animals may indicate a high likelihood of Q fever infection in both domestic animals and humans.

How sensitive and specific is the visual diagnosis of sarcoptic mange in free-ranging Iberian ibexes?

Background

Sarcoptic mange is a broadly distributed parasitic disease caused by Sarcoptes scabiei that affects wild mammals from all over the world, including the Iberian ibex (Capra pyrenaica). Selective culling of the scabietic individuals is the main management measure for disease control in Iberian ibex populations. Although visual identification of mange-compatible lesions is the reference method to decide the target individual, both false negative and positive cases are common in the wild. The aim of this work is to determine the sensitivity (SE), and the specificity (SP) of selective culling after evaluating 403 ibexes hunted in the Sierra Nevada Nature Space for sarcoptic mange control between 2002 and 2015.

Methods

A combination of skin scrapings and potassium hidroxide (KOH) skin digestion was used for sarcoptic mange diagnosis. Generalized linear models (GLM) were used to assess the effects of sex, age (juveniles and adults) and period of the year (wet and dry periods) on the SE and SP of the visual diagnosis method.

Results

The SE obtained for the visual determination of scabietic ibexes was 87.14%, whereas the SP was 60.71%. According to our model selection, SE of the visual diagnosis was explained by the additive effects of age and the period of the year. In fact, SE was lower in juveniles (64.76%) than in adults (94.26%) and during the dry period (73.44%) as compared to the wet period (92.09%). On the other hand, SP was best explained by the GLM including the additive effects of sex and the period of the year. The visual diagnosis of sarcoptic mange resulted less specific in females (22.73%) than in males (74.19%) and during the wet (55.22%) than in the dry period (82.35%).

Conclusions

Maximizing SE and SP is essential to achieving a high rate of removal of affected individuals from the environment without eliminating potentially resistant individuals. Selective culling must be conservative during the wet period and with females due to the lower SP. Conversely, visual diagnosis of scabietic juveniles and during the dry period has to be improved, due to the lower SE.

Coxiella burnetii associated with BVDV (Bovine Viral Diarrhea Virus), BoHV (Bovine Herpesvirus), Leptospira spp., Neospora caninum, Toxoplasma gondii and Trypanosoma vivax in reproductive disorders in cattle

This is a cross-sectional study to assess the presence of antibodies in ruminants against selected pathogens associated with reproductive disorders in cattle in four Brazilian states, including the zoonotic agent Coxiella burnetii. The used tests were Virus Neutralization Assay for IBR and BVD, Microscopic Agglutination Test for Leptospira spp., Indirect Fluorescent Antibody Test (IFAT) for C. burnetii and Toxoplasma gondii, and Enzyme-Linked Immunosorbent Assay for Neospora caninum and Trypanosoma vivax. Seropositivity for C. burnetii was 13.7% with titers from 128 to 131,072; 57.8% for BoHV-1, with titers between 2 and 1,024; 47.1% for BVDV-1a, with titers from 10 to 5,120; 89.2% for N. caninum; 50% for T. vivax; and 52.0% for Leptospira spp., with titers between 100 to 800 (the following serovars were found: Tarassovi, Grippotyphosa, Canicola, Copenhageni, Wolffi, Hardjo, Pomona and Icterohaemorrhagiae); 19.6% for T. gondii with titer of 40. This is the first study that has identified C. burnetii in cattle associated with BoHV and BVDV, N. caninum, Leptospira spp., T. gondii and T. vivax. Thus, future studies should be conducted to investigate how widespread this pathogen is in Brazilian cattle herds.

Serological evidence of Coxiella burnetii infection in cattle and farm workers: is Q fever an underreported zoonotic disease in Ecuador?

Background: Q fever is an underreported zoonotic disease of cattle and men in most countries of the world. Very little information about the prevalence of Coxiella burnetii infection in animals and humans comes from South and Central America and systematic studies are lacking. Methods: A seroprevalence survey for Q fever amongst cattle, farm workers and students was conducted in Ecuador using a commercial ELISA kit. Results: Survey results showed an unexpectedly high prevalence of Coxiella burnetii antibodies in dairy cattle (43%) and in farm workers (34%). In addition, a clinical case in a human of acute Q fever in the convalescent stage was detected. Conclusion: We conclude that the disease is endemic in Ecuador but is overlooked by medical and laboratory personnel. Q fever should be considered a public health issue in Ecuador and further research into the clinical relevance of this infection is recommended.