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PubMed2004

Cattle infestation by Hyalomma ticks and prevalence of Theileria in Hyalomma species in the east of Turkey.

A total of 2388 cattle and 442 shelters, from two provinces (Elazig and Malatya) endemic for tropical theileriosis in the east of Turkey, were studied for Hyalomma tick populations from July 1993 to July 1995 in Elazig and from May 1998 to January 1999 in Malatya. Four thousand five hundred and eighty one of 7455 Hyalomma ticks were collected from cattle, the other ticks (2874) were collected from shelters. All of the ticks collected from shelters were Hyalomma anatolicum anatolicum. Two thousand eight hundred and ninety five (63.1%) of 4581 Hyalomma ticks collected from cattle were H.a. anatolicum. 23.8% (1047/4581), 11.7% (536/4581) and 0.6% (3/4581) of Hyalomma ticks were Hyalomma anatolicum excavatum, Hyalomma detritum and Hyalomma marginatum marginatum, respectively. A total of 5909 Hyalomma adult ticks collected from cattle (3362/5909) and shelters (2447/5909) were dissected and salivary glands were stained with Methylgreen/Pyronin method. Thousand one hundred and fifty (46.9%) of 2447 H.a. anatolicum collected from shelters and 412 (19.1%) of 2147 H.a. anatolicum collected from cattle were positive for Theileria infection. Twenty (2.4%) of 820 H.a. excavatum and 23 (4.6%) of 495 H. detritum collected from cattle were positive. The mean number of infected acini per infected male and female ticks collected from cattle were 11.3 and 22.4 in H.a. anatolicum, 4 and 6.8 in H.a. excavatum, 17.9 and 18.3 in H. detritum, respectively. In H.a. anatolicum collected from shelters, the above rates were 11.8 and 17.6 in male and female ticks, respectively. The prevalence and intensity of Theileria infection was greater in female ticks than in males.

Animals↗
PubMed2004

The high genetic variation of viruses of the genus Nairovirus reflects the diversity of their predominant tick hosts.

The genus Nairovirus (family Bunyaviridae) contains seven serogroups consisting of 34 predominantly tick-borne viruses, including several associated with severe human and livestock diseases [e.g., Crimean Congo hemorrhagic fever (CCHF) and Nairobi sheep disease (NSD), respectively]. Before this report, no comparative genetic studies or molecular detection assays had been developed for this virus genus. To characterize at least one representative from each of the seven serogroups, reverse transcriptase-polymerase chain reaction (RT-PCR) primers targeting the L polymerase-encoding region of the RNA genome of these viruses were successfully designed based on conserved amino acid motifs present in the predicted catalytic core region. Sequence analysis showed the nairoviruses to be a highly diverse group, exhibiting up to 39.4% and 46.0% nucleotide and amino acid identity differences, respectively. Virus genetic relationships correlated well with serologic groupings and with tick host associations. Hosts of these viruses include both the hard (family Ixodidae) and soft (family Argasidae) ticks. Virus phylogenetic analysis reveals two major monophyletic groups: hard tick and soft tick-vectored viruses. In addition, viruses vectored by Ornithodoros, Carios, and Argas genera ticks also form three separate monophyletic lineages. The striking similarities between tick and nairovirus phylogenies are consistent with possible coevolution of the viruses and their tick hosts. Fossil and phylogenetic data placing the hard tick-soft tick divergence between 120 and 92 million years ago suggest an ancient origin for viruses of the genus Nairovirus.

Amino Acid Sequence↗
PubMed1991

Ixodid and argasid ticks. Keys to their identification.

Ticks of the Ixodidae family are important ectoparasites of humans and animals. Of the 80 or so species found in the United States, about 20 are of veterinary importance. Ticks are second only to mosquitoes as carriers of human pathogens. The ixodid (or hard) ticks are the most common and are represented by the genera Ixodes, Haemaphysalis, Boophilus, Rhipicephalus, Amblyomma, and Dermacentor. Accurate identification of the species of ixodid ticks within an area is a prerequisite to control and eradication. Therefore, veterinarians should have a working knowledge of the biology and identity of the more common mammalian-parasitizing ticks in the United States. In the United States, the argasid (or soft) ticks are less common than the ixodid (or hard) ticks. Argasids are represented by the genera Argas, Ornithodoros, and Otobius. Although the overall anatomy of the various species of argasids is similar, their functional approaches to feeding, reproduction, host finding and preference, tick-host behavior, tick relationship to their environment, and disease association vary among species. Accurate identification of the species of argasid ticks within an area is useful in their control.

Animals↗
PubMed2003

Co-feeding studies of ticks infected with Anaplasma marginale.

Ticks often cluster at preferred feeding sites on hosts, and the co-feeding of ticks at the same site has been shown to increase feeding success and the transmission of some pathogens. While the major route of infection of ticks with pathogens is via the bloodmeal during feeding on a parasitemic host, non-systemic transmission of viruses and spirochetes has been shown to occur from infected to uninfected ticks at common feeding sites on uninfected hosts. In this research, two separate studies were done using the tick-borne rickettsial pathogen of cattle, Anaplasma marginale. In one study we tested whether A. marginale could be transmitted non-systemically from infected to uninfected Dermacentor variabilis males while co-feeding on rabbits. Infection of ticks was determined by allowing them to transmission feed on susceptible cattle and by DNA probe and microscopy studies on salivary glands. In the second study, we tested whether the co-feeding of male and female ticks on parasitemic cattle would increase the acquisition and development of A. marginale in males. A. marginale infections in salivary glands were determined by quantitative PCR after the ticks were allowed to transmission feed on susceptible cattle. Non-systemic transmission of A. marginale did not occur from infected and uninfected ticks that fed at the same site on rabbits and, therefore, does not appear to be a means of A. marginale transmission. A. marginale infections in male ticks were not increased while co-feeding with females. Thus, co-feeding of adult Dermacentor spp. does not appear to influence the dynamics of A. marginale transmission.

Anaplasma↗
PubMed2004

Anaplasma marginale (Rickettsiales: Anaplasmataceae): recent advances in defining host-pathogen adaptations of a tick-borne rickettsia.

The tick-borne intracellular pathogen Anaplasma marginale (Rickettsiales: Anaplasmataceae) develops persistent infections in cattle and tick hosts. While erythrocytes appear to be the only site of infection in cattle, A. marginale undergoes a complex developmental cycle in ticks and transmission occurs via salivary glands during feeding. Many geographic isolates occur that vary in genotype, antigenic composition, morphology and infectivity for ticks. In this chapter we review recent research on the host-vector-pathogen interactions of A. marginale. Major surface proteins (MSPs) play a crucial role in the interaction of A. marginale with host cells. The MSP1a protein, which is an adhesin for bovine erythrocytes and tick cells, is differentially regulated and affects infection and transmission of A. marginale by Dermacentor spp. ticks. MSP2 undergoes antigenic variation and selection in cattle and ticks, and contributes to the maintenance of persistent infections. Phylogenetic studies of A. marginale geographic isolates using msp4 and msp1alpha provide information about the biogeography and evolution of A. marginale: msp1alpha genotypes evolve under positive selection pressure. Isolates of A. marginale are maintained by independent transmission events and a mechanism of infection exclusion in cattle and ticks allows for only the infection of one isolate per animal. Prospects for development of control strategies by use of pathogen and tick-derived antigens are discussed. The A. marginale/vector/host studies described herein could serve as a model for research on other tick-borne rickettsiae.

Anaplasma marginale↗
PubMed1996

Detection of four species of Borrelia burgdorferi sensu lato in Ixodes ricinus ticks collected from roe deer (Capreolus capreolus) in The Netherlands.

Roe deer (Capreolus capreolus) were investigated for their value as sentinel animals for Lyme borreliosis in the Netherlands. Serum was obtained from 114 roe deer, and 513 Ixodes ricinus, predominantly females (72%), were obtained from 47 animals (41%). The polymerase chain reaction was used to detect DNA of Borrelia burgdorferi sensu lato in a total of 190 ticks, comprising 106 engorged ticks and 84 non-engorged ticks. Borrelia DNA was detected in 24 engorged ticks (23%) and 26 non-engorged ticks (31%). This difference was not significant (P = 0.25). Four species of B. burgdorferi sensu lato were identified in the ticks. B. burgdorferi sensu stricto, Borrelia garinii, Borrelia afzelii and group VS116. B. afzelii was most commonly found and present in 13 mixed infections, and in 28 single infections. Fifteen sera (13%) contained antibodies to Borrelia spp. Ticks are more appropriate sentinel animals for Lyme borreliosis than roe deer, an important host for I. ricinus. Although the viability of borrelia spirochaetes in engorged ticks collected from roe deer was not assessed, a bloodmeal taken from roe deer did not eliminate borrelia spirochaetes from the tick. The relevance of this finding for transovarial transmission of borrelia spirochaetes in ticks is discussed.

Animals↗
PubMed1997

Detection of Theileria annulata by the PCR in ticks (Acari:Ixodidae) collected from cattle in Mauritania.

We report on the detection of Theileria annulata in infected Hyalomma ticks by the PCR using primers derived from the gene encoding the 30 kDa major merozoite surface antigen (TamsI-1). No inhibition of the PCR was observed and as little as 0.1 pg of parasite DNA, corresponding to 12 sporozoites, could be detected in non-infected tick DNA samples, spiked with T. annulata genomic DNA. Hyalomma dromedarii ticks, fed on a calf experimentally infected with T. annulata, were used to validate the PCR further. The infection rate in the adult ticks, fed as nymphs during the febrile reaction, was high (62%), dropped to zero for 1 day in tick batches that engorged after treatment with Butalex and increased to 30% 2 days later and 38% of the ticks acquired the infection after feeding as nymphs during a carrier state piroplasm parasitaemia of less than 0.1%. As an internal control, 16S tick rDNA sequences could be amplified from T. annulata-negative tick samples. Finally, 202 adult ticks from Mauritania, collected from zebu cattle carrying low levels of Theileria piroplasms, were tested by the PCR. Thirty-eight out of 52 (73%) and 17 out of 30 (57%) H. dromedarii from the Gorgol and Trarza regions, respectively and two out of 30 (7%) Hyalomma marginatum rufipes from the Gorgol region were positive. Hyalomma marginatum rufipes, Rhipicephalus evertsi evertsi and Rhipicephalus guilhoni from the Trarza region were negative. These findings confirm that H. dromedarii is the main vector of T. annulata in Mauritania and that the PCR is a useful method of determining the infection rates in ticks collected from cattle carrying low levels of T. annulata piroplasms.

Animals↗
PubMed2002

Ixodid ticks feeding on humans in South Africa: with notes on preferred hosts, geographic distribution, seasonal occurrence and transmission of pathogens.

This paper records the identities of 558 ixodid ticks feeding on 194 humans in South Africa. These ticks belonged to 20 species in six genera and those most frequently encountered were AmblYomma hebraeum, Haemaphysalis leachi, Hyalomma marginatum rufipes, Hyalomma truncatum, Rhipicephalus appendiculatus, Rhipicephalus gertrudae and Rhipicephalus simus. With the exception of the larvae of R. appendiculatus, the incidents of these ticks feeding on humans correlated well with their seasonal occurrences on preferred hosts. Ticks were also collected at monthly intervals, for 14 consecutive months, from the clothing of a game-guard providing protection for field-workers engaged in the collection, by means of flannel strips, of free-living ticks from the vegetation of four localities in the southern region of the Kruger National Park. In addition, with the exception of 3 months when the particular worker was absent, ticks that fed on one of the field-workers were collected over the same 14-month period. A total of 54,429 free-living ticks belonging to 14 species and six genera were collected from the vegetation at the four localities during this time and 3751 ticks belonging to 11 species and six genera from the clothing of the game-guard. The larvae of A. hebraeum and Boophilus decoloratus were the most numerous of the immature ticks, and H. leachi and R. simus of the adults on both the vegetation and the guard's clothing. Ticks fed on the field-worker on six occasions and 14 were collected, all of which were A. hebraeum larvae.

Adult↗
PubMed2002

Epidemiology and impact of coinfections acquired from Ixodes ticks.

Ixodes scapularis and other ticks in the Ixodes ricinus complex may transmit multiple pathogens, but research on coinfections has been limited. Coinfections occur with varying frequency in ticks, but single infections are more common than dual infections. The proportion of I. scapularis or I. ricinus ticks coinfected with both Borrelia burgdorferi sensu lato and Anaplasma phagocytophila is generally low, ranging from < 1% to 6% in six geographic areas. A higher prevalence of tick coinfection (26%) has been reported in Westchester County, New York. Genetic variants of the human disease-causing strain of A. phagocytophila are present in some tick populations, and they may affect the risk of coinfection or clinical illness. The proportion of Ixodes ticks coinfected with B. burgdorferi and Babesia microti has ranged from 2% in New Jersey to 19% on Nantucket Island, Massachusetts. In humans, cross-sectional seroprevalence studies have found markers of dual infection in 9-26% of patients with a tick-borne infection, but such studies often fail to distinguish simultaneous coinfection from sequential infections. Several studies have prospectively assessed the occurrence of acute coinfection. Among patients with a confirmed tick-borne infection, coinfection rates as high as 39% have been reported. The most commonly recognized coinfection in most of the eastern United States is Lyme borreliosis (LB) and babesiosis, accounting for approximately 80% of coinfections. LB and human granulocytic ehrlichiosis coinfections are less common, occurring in 3-15% of patients with a tick-borne infection in Connecticut or Wisconsin. Studies of clinical outcomes suggest that patients with acute Babesia coinfection have more severe symptoms and a longer duration of illness than patients with LB alone, but the risk of spirochete dissemination is similar. Coinfections can modify the immune response and alter the severity of arthritis in animal models. Future coinfection research should focus on long-term clinical outcomes, the role of genetic variants, immunologic effects, and the potential role of Bartonella species as tick-borne pathogens.

Animals↗
PubMed1990

Computer simulation of Rocky Mountain spotted fever transmission by the American dog tick (Acari: Ixodidae).

A computer model was developed for simulation of the transmission of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever (RMSF), by the American dog tick, Dermacentor variabilis (Say). The model of RMSF was combined with a model for population dynamics of the American dog tick and included simulation of infection and transmission of rickettsiae between ticks and host mammals and transmission of RMSF to humans. The model simulated the effects of biotic and environmental variables such as weather, host density, habitat, transovarial transmission, fecundity of infected ticks, and infectivity level of ticks and mammals. Some parameters in the model were fitted by iterative simulations to produce realistic rates of R. rickettsii infection in adult ticks and small and medium-sized mammal hosts. Parameters also were fitted to yield the historical average number of RMSF cases for Virginia. Comparisons of the simulated and actual number of cases for nine other states indicated a reasonable level of validity for the model. A theoretical tick density threshold of 252 unfed adult ticks/ha for transmission of RMSF was determined from a relationship between rate of transmission to humans and density of ticks. The transmission threshold can be used for additional modeling efforts to study the effects of management technologies on tick densities and RMSF human cases. The model can serve as a framework for modeling other tick-borne diseases such as Lyme disease, babesiosis, and heartwater.

Animals↗
PubMed1994

Host-seeking of blacklegged tick (Acari: Ixodidae) nymphs and adults at the woods-pasture interface.

To clarify the risk of pastured livestock for exposure to Ixodes scapularis Say (Acari: Ixodidae), we estimated the host-seeking activity of nymph and adult blacklegged ticks at the woods-pasture interface on horse farms in Maryland. Parallel linear transects of 100 m length and 1 m width were sampled repeatedly in pastures and adjacent woodland locations during periods of nymph (early summer) and adult (fall and spring) host-seeking activity. Data collected over two successive years indicated that adults were most abundant in ecotonal vegetation at the wood's edge, median values of 6.4 and 2.2 ticks per 100 m2 sample during fall and 1.2 and 0.5 ticks per 100 m2 sample for spring periods. Nymphs were most abundant in the shallow woods location, median values of 4.2 and 35 ticks per 100 m2 sample, followed by the deep woods and wood's edge locations. Host-seeking nymph and adult black-legged ticks also were collected repeatedly in pasture vegetation, median values ranging from 0.2-0.8 ticks per 100 m2 sample, with a progressive decrease in abundance from the fenceline into pasture. Adults and nymphs both were uncommon more than 5 m into pastures, where only two adults and one nymph were captured in 84 (fall and spring) and 24 (summer) 100-m2 samples, respectively. Levels of adult and nymph host-seeking in pasture vegetation were spatially correlated with tick abundance in adjacent woodlands when ticks were numerous; this condition presumably reflects a spillover of ticks from the woodlands-based population. These findings expand knowledge of black-legged tick host-seeking behavior and establish a basis for the exposure of pastured livestock to nymphs and adults.

Aging↗
PubMed1996

Prevalence of spotted fever group rickettsiae in ticks from southern Israel.

The prevalence of spotted fever group rickettsiae was studied in questing ticks collected from southern Israel. Ticks were examined from an agricultural settlement (kibbutz Ze'elim), an endemic site for Mediterranean spotted fever, and from another kibbutz (Re'im) in an adjacent area where the disease has not been reported. Ticks were collected by flagging and CO2 traps from vegetation inside and outside the settlements during 1989/1990 and 1994. In Ze'elim, 98% of the ticks collected were brown dog tick, Rhipicephalus sanguineus (Latreille), whereas in Re'im the predominant species was Rhipicephalus turanicus Pomerantzev (84.6%), with 11.8% of the ticks R. sanguineus and 3.6% Hyalomma excavatum Koch. The presence of rickettsiae in the hemolymph of the ticks was demonstrated by immunofluorescence using polyclonal antibodies made against the human pathogenic Moroccan strain of Rickettsia conorii. Of 549 ticks examined in 1989/1990 from Ze'elim, 7.3% were positive for spotted group rickettsiae, and in Re'im 2.2% of 156 R. turanicus were positive. In 1994, 51 out of 186 (27.4%) ticks in Ze'elim and 3 out of 115 (2.6%) ticks in Re'im were positive. All 20 specimens of H. excavatum were negative for spotted fever group rickettsiae. To our knowledge, this is the 1st report of spotted fever group rickettsiae in R. turanicus from Israel.

Animals↗
PubMed1998

Development of a non-radioactive DNA probe and in situ hybridization for detection of Anaplasma marginale in ticks and cattle.

A non-radioactive DNA probe was developed for detection of Anaplasma marginale in ticks and cattle. The probe was labeled with digoxigenin 11-dUTP by polymerase chain reaction. The probe was tested on bovine blood and was found to be a sensitive and specific detection method for A. marginale in cattle. The DNA probe was then adapted for in situ hybridization (ISH) of A. marginale in Dermacentor andersoni and D. variabilis ticks infected either as nymphs or adults. One-half of each tick was studied with ISH while the other half was examined with light and electron microscopy. In male ticks infected as adults, tick gut cells first became infected with A. marginale while ticks fed on an infected calf, and they remained infected as they transmission fed on a second, susceptible calf. At the onset of transmission feeding, salivary glands became infected with A. marginale. During transmission feeding infection was also observed in interstitial, reproductive, skeletal muscle, fat body and Malpighian tubule tissue, resulting in a generalized A. marginale infection. When adult ticks that acquired infection as nymphs were examined with ISH and microscopy, gut tissues of both D. andersoni and D. variabilis became infected with A. marginale. However, salivary gland infection was seen only in D. variabilis, even though both species of ticks transmitted A. marginale to susceptible calves. A. marginale was not seen with ISH or microscopy in hemocytes collected from both species of ticks and, thus, hemocytes do not appear to play a role in the development of A. marginale in ticks.

Anaplasma↗
PubMed2006

Differential clearance and immune responses to tick cell-derived versus macrophage culture-derived Ehrlichia chaffeensis in mice.

Human monocytic ehrlichiosis is caused by a tick-transmitted rickettsia, Ehrlichia chaffeensis. We recently reported that E. chaffeensis grown in tick cells expresses different proteins than bacteria grown in macrophages. Therefore, we tested the hypothesis that immune responses against E. chaffeensis would be different if the mice are challenged with bacteria grown in macrophages or tick cells. We assessed the E. chaffeensis clearance from the peritoneum, spleen, and liver by C57BL/6J mice using a TaqMan-based real-time reverse transcription-PCR assay. Macrophage-grown E. chaffeensis was cleared in 2 weeks from the peritoneum, whereas the pathogen from tick cells persisted for nine additional days and included three relapses of increasing bacterial load separated by three-day intervals. Tick cell-grown bacteria also persisted in the livers and spleens with higher bacterial loads compared to macrophage-grown bacteria and fluctuated over a period of 35 days. Three-day periodic cycles were detected in T-cell CD62L/CD44 ratios in the spleen and bone marrow in response to infections with both tick cell- and macrophage-grown bacteria and were accompanied by similar periodic cycles of spleen cell cytokine secretions and nitric oxide and interleukin-6 by peritoneal macrophages. The E. chaffeensis-specific immunoglobulin G response was considerably higher and steadily increased in mice infected with the tick cell-derived E. chaffeensis compared to DH82-grown bacteria. In addition, antigens detected by the immunoglobulins were significantly different between mice infected with the E. chaffeensis originating from tick cells or macrophages. The differences in the immune response to tick cell-grown bacteria compared to macrophage-grown bacteria reflected a delay in the shift of gene expression from the tick cell-specific Omp 14 gene to the macrophage-specific Omp 19 gene. These data suggest that the host response to E. chaffeensis depends on the source of the bacteria and that this experimental model requires the most natural inoculum possible to allow for a realistic understanding of host resistance.

Animals↗
PubMed1998

Acquisition and transmission of the agent of human granulocytic ehrlichiosis by Ixodes scapularis ticks.

The purpose of the present study was to investigate the transmission of a human isolate of the agent of human granulocytic ehrlichiosis (HGE agent) from infected mice to larval ticks and to examine the population kinetics of the HGE agent in different stages of the tick life cycle. The HGE agent was quantitated by competitive PCR with blood from infected mice and with Ixodes scapularis ticks. The median infectious dose for C3H mice was 10(4) to 10(5) organisms when blood from an infected severe combined immunodeficient mouse was used as an inoculum. Uninfected larval ticks began to acquire infection from infected mice within 24 h of attachment, and the number of HGE agent organisms increased in larval ticks during feeding and after detachment of replete ticks. Molted nymphal ticks, infected as larvae, transmitted infection to mice between 40 and 48 h of attachment. Onset of feeding stimulated replication of the HGE agent within nymphal ticks. These studies suggest that replication of the HGE agent during and after feeding in larvae and during feeding in nymphs is a means by which the HGE agent overcomes inefficiencies in acquisition of infection by ticks and in tick-borne transmission to mammalian hosts.

Animals↗
PubMed2004

A prospective cross-over field trial shows protection of lemon eucalyptus extract against tick bites.

Ixodes ricinus can transmit several microorganisms, out of which Borrelia burgdorferi and tick-borne encephalitis (TBE) virus are the most important pathogens in humans. A lemon eucalyptus extract (Citriodiol) has been shown to be a natural repellent against mosquitoes, stable flies, and midges. We have investigated whether the use of the extract would reduce the number of attached I. ricinus ticks in humans. A volunteer sample of 111 individuals was recruited among healthy, outdoor active adults living in two highly I. ricinus-infested areas. They were randomly divided into two groups: one group applied the Citriodiol spray daily for 2 wk to the lower extremities, whereas the other group was instructed not to use any type of repellent on any part of the body. After 2 wk, the scheme was reversed. All volunteers filled in a daily diary, giving information about outdoor activities and the number of observed, attached, or not yet attached ticks, including the anatomical location of the ticks found. Forty-two attached ticks were reported during the weeks when the Citriodiol spray was used, and 112 were reported when it was not. The median number of reported attached ticks per person decreased from 1.5 (range, 0-9) to 0.5 (range, 0-2; P < 0.05) during the weeks when the repellent was used. The number of reported attached ticks noted below the waist was 13/42 (31%) during the period when the spray was used and 73/112 (65%) when no spray was used (P < 0.001). No evident redistribution of attached ticks from protected areas to unprotected areas was seen. Citriodiol may become a useful means in reducing the number of tick bites and thereby tick-borne infections, although additional studies are warranted.

Adult↗
PubMed2005

Efficacy of a collar impregnated with amitraz and pyriproxyfen for prevention of experimental tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs.

OBJECTIVE: To compare the efficacy of collars impregnated with 9% amitraz or 9% amitraz and 0.5% pyriproxyfen (PPF) for control of newly established tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs and determine whether egg production by surviving female ticks was decreased. DESIGN: Prospective study. ANIMALS: 72 dogs. PROCEDURE: Dogs were fitted with 1 of 3 test collars impregnated with amitraz, amitraz and PPF, or only excipients (untreated controls). In 3 trials corresponding to each of the 3 tick species, dogs were infested with 150 unfed adult ticks on days 8, 10, 13, and 18. The number of feeding female ticks was recorded on days 10, 13, 18, and 28. Surviving females were weighed and permitted to oviposit under controlled conditions. RESULTS: Collars impregnated with amitraz and PPF decreased tick loads as efficiently as collars containing amitraz alone. Inclusion of PPF into the collar did not significantly decrease the efficacy of amitraz. The few female ticks that survived after feeding on dogs treated with collars containing PPF were unable to oviposit. CONCLUSIONS AND CLINICAL RELEVANCE: Collars impregnated with amitraz were efficient in preventing tick infestations in dogs but did not inhibit oviposition in the few surviving female ticks. Incorporation of PPF into the amitraz-impregnated collar resulted in impairment of the reproductive ability of ticks.

Animals↗
PubMed1985

Experimental studies on the replication and dissemination of Qalyub virus (Bunyaviridae: Nairovirus) in the putative tick vector, Ornithodoros (Pavlovskyella) erraticus.

A study was undertaken to determine if the argasid tick, Ornithodoros (Pavlovskyella) erraticus, can serve as a biological vector of Qalyub (QYB) virus. The suckling mice used as viremic vertebrate hosts were acceptable hosts for all feeding stages of this tick and developed relatively high titered viremias (4.4-6.5 log10PFU/ml) 24-120 hr post intracerebral inoculation. Larval, nymphal, and adult ticks became orally infected with QYB virus after ingesting 4.4-6.4 log10PFU/ml. The overall infection rate for all experiments was 67/205 and virus was recovered up to day 179 postfeeding. Incubation of known quantities of QYB virus with uninfected triturated tick tissues did not result in any appreciable virus inactivation. QYB viral antigen was detected by immunofluorescence primarily in the tick midgut posterior diverticula cells. First and second instar nymphs orally infected as larvae did not individually transmit QYB virus to suckling mice; however they successfully transmitted the virus when feeding in groups of 11-20 per mouse. Three out of fourteen of the orally-infected male and female ticks individually transmitted QYB virus orally to suckling mice. Organ titrations of ticks orally exposed to QYB virus demonstrated virus primarily in midgut tissues; dissemination to other organ systems was discovered in only 1 tick after 142 days extrinsic incubation. Vertical transmission of virus from infected female ticks to progeny was not demonstrated. Four of the 39 ticks in our colony were infected with a spirochete; presumably, Borrelia crocidurae. O. (P.) erraticus apparently satisfies the conditions that would implicate this species as a biological vector of QYB virus and is the only known arthropod from which this virus has been isolated in nature.

Animals↗