Tick Infection Rates Research Articles

Detection of Theileria annulata by the PCR-RFLP in ticks (Acari, Ixodidae) collected from cattle in West and North-West Iran

AbstractThe presence of potential vectors, ticks, and susceptible hosts of bovine malignant theileriosis in all parts of Iran pose a real threat to food animal industry. The present study was conducted to determine the infection rate of ticks collected from naturally occurring bovine theileriosis in West and North-West Iran. Two hundred and thirty seven cattle suspected of suffering from theileriosis were investigated for the presence of Theileria annulata in the blood smears and any tick species on their body. In this study, 402 ticks were obtained from 99 cattle. The examination of 402 ticks by polymerase chain reaction (PCR) using primers derived from the gene encoding heat shock protein70 (Hsp70) revealed that 39.9% of Hyalomma anatolicum anatolicum, 3.5% of H. asiaticum asiaticum, and 18.2% H. anatolicum excavatum, were infected with T. annulata. The results suggest that H. a. anatolicum may play a major role in transmission of T. annulata infection in Iran. Finally, digestion of the PCR products of T. annulata with two different restriction enzymes produced only a single pattern.

Geographic and Temporal Variations in Population Dynamics ofIxodes ricinusand AssociatedBorreliaInfections in The Netherlands

In a countrywide investigation of the ecological factors that contribute to Lyme borreliosis risk, a longitudinal study on population dynamics of the sheep tick Ixodes ricinus and their infections with Borrelia burgdorferi sensu lato (s.l.) was undertaken at 24 sites in The Netherlands from July 2006 to December 2007. Study sites were mature forests, dune vegetations, or new forests on land reclaimed from the sea. Ticks were sampled monthly and nymphal ticks were investigated for the presence of Borrelia spp. I. ricinus was the only tick species found. Ticks were found in all sites, but with significant spatial and temporal variations in density between sites. Peak densities were found in July and August, with lowest tick numbers collected in December and January. In some sites, questing activities of I. ricinus nymphs and adults were observed in the winter months. Mean monthly Borrelia infections in nymphs varied from 0% to 29.0% (range: 0%-60%), and several sites had significantly higher mean nymphal Borrelia infections than others. Four genospecies of Borrelia burgdorferi s.l. were found, with B. afzelii being dominant at most sites. Borrelia infection rates in nymphal ticks collected in July, September, and November 2006 were significantly higher (23.7%, p<0.01) than those in the corresponding months of 2007 (9.9%). The diversity in Borrelia genospecies between sites was significantly different (p<0.001). Habitat structure (tree cover) was an effective discriminant parameter in the determination of Borrelia infection risk, as measured by the proportion of nymphal ticks infected with B. burgdorferi s.l. Thickness of the litter layer and moss cover were positively related to nymphal and adult tick densities. The study shows that Borrelia-infected ticks are present in many forest and dune areas in The Netherlands and suggests that in such biotopes, which are used for a wide variety of recreational activities, the infection risk is high.

Borrelia burgdorferi sensu lato in Ixodes ricinus ticks collected from migratory birds in Southern Norway

BackgroundBorrelia burgdorferi sensu lato (s.l.) are the causative agent for Lyme borreliosis (LB), the most common tick-borne disease in the northern hemisphere. Birds are considered important in the global dispersal of ticks and tick-borne pathogens through their migration. The present study is the first description of B. burgdorferi prevalence and genotypes in Ixodes ricinus ticks feeding on birds during spring and autumn migration in Norway.Methods6538 migratory birds were captured and examined for ticks at Lista Bird Observatory during the spring and the autumn migration in 2008. 822 immature I. ricinus ticks were collected from 215 infested birds. Ticks were investigated for infection with B. burgdorferi s.l. by real-time PCR amplification of the 16S rRNA gene, and B. burgdorferi s.l. were thereafter genotyped by melting curve analysis after real-time PCR amplification of the hbb gene, or by direct sequencing of the PCR amplicon generated from the rrs (16S)-rrl (23S) intergenetic spacer.ResultsB. burgdorferi s.l. were detected in 4.4% of the ticks. The most prevalent B. burgdorferi genospecies identified were B. garinii (77.8%), followed by B.valaisiana (11.1%), B. afzelii (8.3%) and B. burgdorferi sensu stricto (2.8%).ConclusionInfection rate in ticks and genospecies composition were similar in spring and autumn migration, however, the prevalence of ticks on birds was higher during spring migration. The study supports the notion that birds are important in the dispersal of ticks, and that they may be partly responsible for the heterogeneous distribution of B. burgdorferi s.l. in Europe.

Stability and Tick Transmission Phenotype ofgfp-TransformedAnaplasma marginalethrough a CompleteIn VivoInfection Cycle

We tested the stability and tick transmission phenotype of transformed Anaplasma marginale through a complete in vivo infection cycle. Similar to the wild type, the gfp-transformed A. marginale strain established infection in cattle, a natural reservoir host, and persisted in immune competent animals. The tick infection rates for the transformed A. marginale and the wild type were the same. However, there were significantly lower levels of the transformed A. marginale than of the wild type in the tick. Despite the lower levels of replication, ticks transmitted the transformant. Transformants can serve as valuable tools to dissect the molecular requirements of tick colonization and pathogen transmission.

Prevalence and Molecular Characterization of Tick-Borne Encephalitis Virus inIxodes ricinusTicks Collected in Slovenia

The hard tick Ixodes ricinus is the principal vector of tick-borne encephalitis virus (TBEV) in Slovenia; but until now, there was no information about the prevalence of TBEV infection in Slovenian ticks. We conducted a 2-year survey in 2005 and 2006, during which we were collecting I. ricinus ticks monthly in eight different locations of Slovenia. A total of 4777 I. ricinus ticks were collected: 1515 in year 2005 and 3262 in year 2006. The collected ticks were pooled into groups from which total RNA was extracted. Viral RNA was detected using real-time RT-polymerase chain reaction (PCR). Ticks infected with TBEV were found in six of eight locations. Viral RNA was detected in 8 of the 230 pools of ticks collected in 2005 and in 14 of the 442 pools collected in 2006. Prevalence of TBEV infection in Slovenian ticks was determined as 0.47%: 0.54% in 2005 and 0.43% in 2006. The detected infection rate in ticks significantly correlates with the TBEV incidence rates in selected areas. Using the method of sequencing, we have confirmed that the TBEV in ticks is genetically related to the TBEV in Slovenian patients.

PREVALENCE AND GENETIC HETEROGENEITY OF BORRELIA BURGDORFERI SENSU LATO IN IXODES TICKS IN BELGIUM

Borrelia burgdorferi sensu lato is a genetically diverse group of spirochetes that includes the agent of Lyme borreliosis in which genospecies tend to be associated with specific clinical features. The aim of the study was to determine the prevalence and genetic diversity of Borrelia burgdorferi sensu lato in 524 ticks collected in woods of a western province of Belgium. Presence of spirochetes in ticks was determined by phase contrast microscopy. The mean infection rate of ticks was 12.0%. Variability was observed in the prevalence of infection among the five sites examined, ranging from 2.8 to 21.6%. Identification to genospecies was determined by PCR and sequencing. The most common genomospecies were Borrelia afzelii (55%) and Borrelia garinii (21%). For the first time in Belgium, we detected Borrelia valaisiana and Borrelia spielmanii, representing 14% and 2%, respectively. Borrelia burgdorferi sensu stricto counted only for 2%. Co-infections were present in 8% of ticks. We emphasize the need for clinical studies to assess the prevalence of specific genospecies-related clinical manifestations of Lyme borreliosis in Belgium.

Prevalence and Seasonality of Tick-Borne Pathogens in Questing Ixodes ricinus Ticks from Luxembourg

In Europe, ixodid ticks are important arthropod vectors of human and animal pathogens, but comprehensive studies of the prevalence of all relevant pathogens in Central Europe are scarce. As a result of ecological changes, the incidences of tick-borne infections are expected to increase. In this study, 1,394 nymphal and adult Ixodes ricinus ticks sampled monthly during the active season from 33 ecologically distinct collection sites throughout Luxembourg were screened for all human tick-borne pathogens relevant in Central Europe. Species were identified by sequence analysis of detection PCR amplicons. Mean infection rates of ticks were 11.3% for Borrelia burgdorferi sensu lato, 5.1% for Rickettsia sp., 2.7% for Babesia sp., and 1.9% for Anaplasma phagocytophilum. No tick was found to be infected with Coxiella sp., Francisella tularensis subsp., or Tick-borne encephalitis virus (TBEV). A total of 3.2% of ticks were infected with more than one pathogen species, including mixed Borrelia infections (1.5%). Seasonal variations of tick infection rates were observed for Borrelia, Babesia, and Anaplasma, possibly reflecting a behavioral adaptation strategy of questing ticks. A positive correlation between the grade of urbanization and Borrelia infection rate of ticks was observed, suggesting an established urban zoonotic cycle. We also found Hepatozoon canis (0.1%) and Bartonella henselae (0.3%), which so far have not been found in questing Ixodes ricinus ticks in Central Europe.

Blood Meal Analysis to Identify Reservoir Hosts forAmblyomma americanumTicks

Efforts to identify wildlife reservoirs for tick-borne pathogens are frequently limited by poor understanding of tick-host interactions and potentially transient infectivity of hosts under natural conditions. To identify reservoir hosts for lone star tick (Amblyomma americanum)-associated pathogens, we used a novel technology. In field-collected ticks, we used PCR to amplify a portion of the 18S rRNA gene in remnant blood meal DNA. Reverse line blot hybridization with host-specific probes was then used to subsequently detect and identify amplified DNA. Although several other taxa of wildlife hosts contribute to tick infection rates, our results confirm that the white-tailed deer (Odocoileus virginianus) is a reservoir host for several A. americanum-associated pathogens. Identification of host blood meal frequency and reservoir competence can help in determining human infection rates caused by these pathogens.

Correlation between Tick Density and Pathogen Endemicity, New Hampshire

To assess the endemicity of tick-borne pathogens in New Hampshire, we surveyed adult tick vectors. Pathogens were more prevalent in areas of high tick density, suggesting a correlation between tick establishment and pathogen endemicity. Infection rates in ticks correlated with disease frequency in humans.

Amblyomma variegatum Ticks and Heartwater on Three Caribbean Islands

Amblyomma variegatum tick infestation, tick infection by Ehrlichia ruminantium (ER), and ER genetic diversity were studied in the Caribbean Islands of Guadeloupe, Marie-Galante, and Antigua between 2003 and 2005. Nested PCR for pCS20 was used to detect ER, while ER strains were characterized by sequencing or by restriction fragment length polymorphism (RFLP) profiles of map-1 PCR products. In 2003 in Guadeloupe, the prevalence of tick-infested herds was 35.6%. In Marie-Galante 79.1% of herds in 2003 and 73.8% in 2005 were infested, while only an average of 2.2% of the herds were infected in Antigua between this same period. In Marie-Galante, 19.1% of ticks were ER positive, and ER-infected ticks were found in 33.3% of the herds. In Antigua only 5.8% of the ticks were ER positive. High ER tick infection rate combined with a very high level of tick infestation highlight the risk of heartwater in Marie-Galante and Guadeloupe more than in Antigua. The three islands still represent a reservoir for tick and heartwater in the Caribbean. Nine different African and Caribbean map-1 ER genotypes were identified. This diversity was observed even in restricted areas, and identical map-1 genotypes were observed on all three islands. This high genetic diversity of ER strains suggests that there was a simultaneous introduction of several strains from African countries into the Caribbean region.

Spread of ticks and tick-borne diseases in Germany due to global warming

Tick-transmitted diseases like tick-borne encephalitis and Lyme Borreliosis have been well known in Germany for decades. Global climate changes may influence the emergence and reemergence of diseases. Ongoing research now gives an additional focus on other tick-borne pathogens such as Coxiella burnetii, Rickettsia conorii, Anaplasma phagocytophilum and Babesia spp., the causative agents of Q-fever, Mediterranean spotted fever, Anaplasmosis and Babesiosis, respectively. The epidemiology of these pathogens was investigated on ticks as well as on rodents, the main hosts. Therefore adults of Dermacentor spp. (n = 862) and rodents (n = 119) were collected and examined for the existence of C. burnetii and Rickettsia spp. by polymerase chain reaction (PCR). In none of the ticks and rodents C. burnetii could be detected, in contrast to Rickettsia spp. where the infection rate in ticks was about 20%. Over and above that, nymphs and adults of Ixodes ricinus were also collected and investigated by PCR for A. phagocytophilum (n = 5,424), Rickettsia helvetica (n = 1,187) and Babesia spp. (n = 3,113). Thereby infection rates of 1%, 8.9% and 1%, respectively, could be determined. The prevalence in rodents was 5.3% for A. phagocytophilum and 0.8% for Babesia microti. None of the rodents was R. helvetica positive.

Experimental Infection of OpossumsDidelphis auritabyRickettsia rickettsiiand Evaluation of the Transmission of the Infection to TicksAmblyomma cajennense

The present study evaluated the infection of opossums (Didelphis aurita) by Rickettsia rickettsii and their role as amplifier hosts for horizontal transmission of R. rickettsii to Amblyomma cajennense ticks. Three groups of opossums were evaluated: on day 0, group 1 (G1) was inoculated intraperitoneally with R. rickettsii; group 2 (G2) was infested by R. rickettsii-infected ticks; and group 3 (G3) was the uninfected control group. Opossum rectal temperature was measured daily. Blood samples were collected every 2 to 4 days during 30 days, and used to (1) inoculate guinea pigs intraperitoneally; (2) extract DNA followed by real-time polymerase chain reaction (PCR) targeting the rickettsial gene gltA; (3) study hematology; (4) detect R. rickettsii-reactive antibodies by indirect immunofluorescence assay (IFA). Blood was also collected every 10 days from days 30 to 180, to be tested by serology. Opossums were infested by uninfected A. cajennense larvae and nymphs from days 3 to 15. Engorged ticks were collected and allowed to molt in an incubator. Thereafter, the subsequent flat ticks were allowed to feed on uninfected rabbits, which were tested for seroconversion by IFA. Samples of flat ticks were also tested by real-time PCR. All G1 and G2 opossums became infected by R. rickettsii, as demonstrated by realtime PCR or/and guinea pig inoculation, but they showed no clinical abnormality. Rickettsemia was first detected at days 2 to 8, lasting intermittently till days 1 to 30. Approximately 18% and 5% of the flat ticks previously fed on G1 and G2 opossums, respectively, became infected by R. rickettsii, but only the rabbits infested with G1-derived ticks seroconverted. The study demonstrated that R. rickettsii was capable of infecting opossums without causing illness and developing rickettsemia capable of causing infection in guinea pigs and ticks, although the infection rate in ticks was low.

Detection and genotyping of Borrelia burgdorferi in the trans-border area between Italy and Slovenia and evaluation of co-infection with Anaplasma phagocytophilum in ticks

The present monitoring project aimed at detecting the prevalence of Borrelia burgdorferi in ticks in the Friuli Venezia Giulia (FVG) Region (north-eastern Italy) and along the western border of Slovenia and to determine the Borrelia circulating genospecies. Since Anaplasma phagocytophilum had been found in the study area, we also evaluated the co-infection of the two pathogens in tick ( Ixodes ricinus) populations. The ticks collected during 2005 in 15 sites located in the study area were analyzed to detect the presence of B. burgdorferi by amplifying the intergenic spacer 5S–23S. Genotyping was performed using a new nested-PCR–RFLP method, targeting the ospA gene. A. phagocytophilum was searched for by amplifying the epank1 gene. The average infection rate of ticks with B. burgdorferi varied from 11.8% to 45.5% in the different study sites. A. phagocytophilum was present in the 1.6% of the investigated ticks and apparently homogeneously distributed. The percentage of co-infection with B. burgdorferi sensu lato was 3.4%. At least four different Borrelia species were found: B. afzelii (54.9%), B. garinii (31.7%), B. burgdorferi sensu stricto (6.1%), and 4.9% of a species unidentified whose phylogenetic analysis showed no similarity with any of the known Borrelia genospecies.

Zoonotic Pathogens inIxodes scapularis, Michigan

Zoonotic Pathogens in<i>Ixodes scapularis</i>, Michigan

Molecular detection of Ehrlichia ruminantium infection in Amblyomma variegatum ticks in The Gambia

In West Africa, losses due to heartwater disease are not known because the incidence/prevalence has not been well studied or documented. To develop a diagnostic tool for molecular epidemiology, three PCR-based diagnostic assays, a nested pCS20 PCR, a nested map1 PCR and a nested reverse line blot (RLB) hybridization assay, were evaluated to determine their ability to detect infection in vector ticks, by applying them simultaneously to A. variegatum field ticks to detect Ehrlichia ruminantium, the causative agent of heartwater. The nested pCS20 PCR assay which amplified the pCS20 gene fragment showed the highest detection performance with a detection rate of 16.6%; the nested map1 PCR, which amplified the gene encoding the major antigenic protein1 (map1 gene) showed a detection rate of 11% and the RLB, based on the 16S rDNA sequence of anaplasma and ehrlichial species, detected 6.2%. The RLB, in addition, demonstrated molecular evidence of Ehrlichia ovina, Anaplasma marginale and Anaplasma ovis infections in The Gambia. Subsequently, the pCS20 assay was applied to study the prevalence and distribution of E. ruminantium tick infection rates at different sites in five divisions of The Gambia. The rates of infection in the country ranged from 1.6% to 15.1% with higher prevalences detected at sites in the westerly divisions (Western, Lower River and North Bank; range 8.3-15.1%) than in the easterly divisions (Central River and Upper River; range 1.6-7.5%). This study demonstrated a gradient in the distribution of heartwater disease risk for susceptible livestock in The Gambia which factor must be considered in the overall design of future upgrading programmes.

Comparison of Duplex PCR and Microscopic Techniques for the Identification of Babesia bigemina and Babesia bovis in Engorged Female Ticks of Boophilus microplus

A single-step duplex polymerase chain reaction (PCR) technique and traditional microscopic examination of haemolymph smears were used to detect Babesia bigemina and/or Babesia bovis infection in engorged female ticks of Boophilus microplus recovered from calves raised in an endemic area of the State of Minas Gerais, Brazil. In the PCR amplification of tick-derived DNA, pairs of oligonucleotide primers specific for a 278-bp sequence from B. bigemina and for a 350-bp sequence from B. bovis were used conjointly. The microscopic examination of haemolymph revealed that 16.7% of the engorged ticks were infected with Babesia spp., although no significant differences (rho > 0.05) were found in the infection rate of ticks collected from calves of different age groups. PCR analysis showed that 77.8% of the engorged ticks whose haemolymph contained sporokinetes were infected with B. bigemina, 7.8% with B. bovis and 14.4% with both protozoan species. However, the PCR assay further revealed that, amongst the engorged female ticks whose haemolymph was apparently negative for the presence of sporokinetes, 15.6% were infected with B. bigemina, 2.2% with B. bovis and 10.0% with both species. The duplex PCR method is thus more efficient and sensitive than the microscopic assay and also permits facile identification of the protozoa species present in engorged female ticks.

Risk for infection by Lyme disease cause in green surfaces maintenance workers in Belgrade

Lyme disease (LD) is a cosmopolitan disease from the group of zoonoses that in humans can affect skins, joints, heart and/or nervous system. Research conducted in endemic areas, shows not only that the population, which lives or works in tick habitats, is in a high risk for getting infected by LD cause, but also that every enviroment itself is specific in regard to both vectors and B. burgdoferi species. In our enviroment, research of seropositivity to B. bugdorferi in persons exposed to vectors of LD have not been conducted. The aim of this study was to determine whether there was a higher risk for getting B. burgdofei infection in the fieldworks of JKP "Zelenilo Beograd" than in other persons. Risk for getting LD in the fieldworkers of JKP "Zelenilo Beograd" (park-maintanance company) was determined according to seropositivity, the number and infection rate of LD vectors, and entomological risk index (ERI) value. Serum samples of 34 fieldworkers ofJKP "Zelenilo Beograd", and 35 persons of the control group, were tested for the presence of specific IgM and IgG anti-B. burgdofedi antibodies by using ELISA test In the research localities, the number of ticks was estimated by using the flag hours method, and tick infection rate was determined by dark field microscopy, with magnification rate of 400x. The data were analyzed statistically using chi(2) test, and Pearson's correlation analysis. Out of 34 fieldworkes serum samples, 8 (23.5%) were positive on anti-B. buagdorfei antibody presence, while in the control group only one (2.9%/0) sample was positive (p < 0,05). Seropositivity rate varied from 0-66.6% among localities. Flag hours value among the localities ranged from 8.2-29.9, and tick infection rate ranged from 10.8-22.3%. ERI value was 0.03-0.15. Correlation between flag hour rate and seropositivity, tick infection rate and seropositivity, and also ERI and seropositivity was established. Frequency of B. burgdorferi seropositivity was significantly higher in green-surface maintenance workers, than in the control group not exposed to these habitats. A significant correlation was found between anti-B. burgdofedi antibodies findings and the number of ticks, tick infection rate, and ERI. The results obtained in our study indicate that there was a significantly higher risk for getting LD cause in the fieldworkers than in the control group.

Assessing peridomestic entomological factors as predictors for Lyme disease

The roles of entomologic risk factors, including density of nymphal blacklegged ticks (Ixodes scapularis), prevalence of nymphal infection with the etiologic agent (Borrelia burgdorferi), and density of infected nymphs, in determining the risk of human Lyme disease were assessed at residences in the endemic community of South Kingstown, RI. Nymphs were sampled between May and July from the wooded edge around 51 and 47 residential properties in 2002 and 2003, respectively. Nymphs were collected from all residences sampled. Tick densities, infection rates, and densities of infected nymphs were all significantly higher around homes reporting Lyme disease histories in 2003, while only infection rates were significantly higher in 2002. However, densities of infected nymphs did not significantly predict the probability of Lyme disease at a residence (by logistic regression) in either year. There were no significant differences in entomologic risk factors between homes with state-confirmed Lyme disease histories and homes with self-reported cases (not reported to the state health department). Therefore, although entomologic risk factors tended to be higher at residences with cases of Lyme disease, entomological indices, in the absence of human behavior measures, were not useful predictors of Lyme disease at the scale of individual residences in a tick-endemic community.

Epidemiological Characteristics and Clinical Manifestations of Lyme Borreliosis in Croatia

The goal was to show the epidemiological characteristics and clinical manifestations of Lyme borreliosis in Croatia. Data on registered Lyme borreliosis cases were analyzed and the most common clinical manifestations of the disease, based on meta-analysis of the data collected, are described. A total of 3,317 cases were reported from 1987 to the end of 2003. Northwestern Croatia is an area in which Lyme borreliosis is endemic, but the disease has also been recorded in the other parts of the country, with the exception of the area south of Zadar. The clinical picture of Lyme borreliosis in Croatia is dominated by erythema migrans, followed by neurological manifestations. The diversified clinical picture is consistent with reports from other European countries, as is the isolation of Borrelia afzelii and Borrelia garinii, which are causally related to these forms of the disease. Tick density and tick infection rates of Borrelia burgdorferi have not yet been investigated in the part of Croatia free from the occurrence of Lyme borreliosis.

Acquisition and transmission of Theileria parva by vector tick, Rhipicephalus appendiculatus

In order to investigate the transmission dynamics of Theileria parva ( T. parva) by the brown ear tick, Rhipicephalus appendiculatus ( R. appendiculatus), under experimental conditions, detection of T. parva in ticks and cattle was performed by a quantitative real-time PCR assay. A calf inoculated with a T. parva mixture became PCR-positive for T. parva infection on day 8 post-inoculation, and subsequently, nymphal ticks were introduced and maintained to feed on the infected calf for 6 days. Engorged nymphs were collected daily and allowed to molt into adults, and overall, 70.8% (121/171) of the adult ticks acquired the T. parva infection. Furthermore, the T. parva infection rate in ticks under field conditions was monitored by real-time PCR in R. appendiculatus ticks collected from a traditionally managed pastoral land of Zambia, on which Sanga breed cattle are traditionally reared and the area has endemic East Coast fever (ECF). A total of 70 cattle were randomly selected in the same area and 67 (95.7%) were found to be serologically positive for R. appendiculatus tick antigen (RIM36). Twenty-nine (43.3%) of the 67 serologically positive cattle were real-time PCR-positive for T. parva, although no piroplasms could be detected in the blood smears. Unexpectedly, out of 614 R. appendiculatus nymphal and adult ticks collected by flagging vegetation, 4.1% were positive for T. parva DNA. However, since the rate of transmission of T. parva from infected cattle to ticks and vice versa and the serological evidence of exposure to R. appendiculatus ticks in naturally exposed cattle were relatively high, it would be wise in such a case to consider vector control as well as vaccination against ECF as control measures.