Maturation of Theileria sergenti in salivary glands of Haemaphysalis longicornis induced by temperature stimulation

The parthenogenetic Haemaphysalis longicornis larvae engorged on cattle naturally infected with Theileria sergenti were reared at 24 degrees C. The resultant nymphal ticks were incubated at 37 degrees C to clear the effect of incubation on the development and maturation of sporozoites. The sporozoites in the salivary glands of the nymphal ticks exposed to 37 degrees C for 16 days were observed by the methyl green pyronin staining method. The ticks exposed to 37 degrees C were ground up in a mortar and the supernatant of the tick suspension in PBS was inoculated into cattle. The cattle showed parasitemia and specific antibody response 18 days after inoculation. Consequently, the parasites in the tick salivary glands became infective to cattle by incubating infected. H. longicornis nymphs at 37 degrees C.     

The effect of the bont tick (Amblyomma hebraeum) on the weight gain of Africander steers

The effects of the bont tick Amblyomma hebraeum on the productivity of cattle need to be quantified in order to design economically optimal control programs. Liveweight gains (LWGs) of three groups of Africander steers, maintained in the same pasture and exposed to zero, medium or high numbers of larvae, nymphs and adults of the tick, were measured. Larvae and nymphs had no significant effect on LWG but adults had a large, statistically significant effect (P less than 0.05). The tick-free group had an average LWG of 20 kg more than the heavily infested group after 3.5 months. No mortality was recorded from ticks or tick-borne diseases during the experiment. There was no relationship between the number of engorging adult female ticks counted and loss of LWG of individual animals. The latter suggests that exposure to ticks as well as engorgement by female ticks causes losses. The loss per adult female that completed engorgement was estimated, by relating the LWGs of individual animals to their tick infestations, to be 4 +/- 2 g per adult female tick. An alternative estimate, made by comparing the average LWG and tick infestations of each treatment group, was equal to 10 +/- 4 g. This latter estimate includes the effect of challenge (and rejection) as well as tick feeding and so was accepted as giving the best estimate. Screw-worm fly (Chrysomya bezziana) struck an average of 7.5% of the cattle infested with ticks in any week but the effects on the productivity of the cattle were minimized by immediate treatment. There was a significant, positive correlation between the incidence of screw-worm fly strike and the numbers of adult ticks counted on the experimental animals. The results provide data for calculating losses caused by A. hebraeum in different parts of its geographical range.     

Feeding predilection of Gulf Coast tick, Amblyomma maculatum Koch, nymphs on cattle

Gulf Coast tick nymphs successfully attached and fed on cattle after being freely released. Six Hereford heifers were each infested with approximately 2000 Gulf Coast tick nymphs, three with a strain originating from Refugio Co., TX, and three with ticks from Osage Co., KS by free release on the head and legs to simulate field acquisition of questing nymphs. Two re-infestations were conducted, the first at 7 days and the second at 28 days. Nymph dispersal was estimated by daily inspection of 22 body areas and removal of engorging ticks from the third to the fifth days post-infestation. Total recovery of engorging Texas nymphs was 3.0, 10.2, and 0% and Kansas nymphs was 21.5, 3.3, and 0% for infestations one, two and three, respectively. Immunological resistance to tick infestation expressed as cellular hypersensitivity was evident against Kansas nymphs in the second infestation and against both tick strains in the third infestation. Ticks removed from the withers, midline, and tail-head areas accounted for 68% of the total nymphs recovered in the first two infestations. Within these areas, nymphs were observed to aggregate in small spots where the hair was less dense or naturally parted and the remainder were found scattered in dense hair.     

Life cycle of the tick Amblyomma parvum Aragão, 1908 (Acari: Ixodidae) and suitability of domestic hosts under laboratory conditions

Amblyomma parvum is a widespread Neotropical tick found on several domestic animals and is known to harbor a Rickettsia species of yet unknown pathogenicity. However its life cycle on, and suitability of, several of these hosts has not been described. In this work the biology of A. parvum is presented when fed on seven domestic hosts (chicken, dog, rabbit, horse, guinea pig, cattle and goat). The complete life cycle of the tick varied from 96.8 to 102 days. Highest engorgement weight of larvae was from ticks fed on horses and that of nymphs from guinea pigs. Highest larval yield was from guinea pigs and that of nymphs from horses. Engorged female and egg mass weights, yield and conversion of female weight to eggs rates were the highest in dog ticks and the lowest in goat ticks. The highest egg hatching rate was seen in ticks from dogs and the lowest in ticks from cattle. Overall it was seen that dogs were the best host for adult A. parvum ticks, and guinea pigs for immatures. Horses were also shown to be a good host for all tick stages. It can thus be affirmed that A. parvum is a host generalist tick, and its distribution is probably determined by environmental requirements rather than by hosts.     

Histopathology of attachment sites of Amblyomma variegatum and Rhipicephalus appendiculatus on zebu cattle of varying resistance to ticks.

Mature, unimproved East African Zebu cattle (Bos indicus) naturally exposed to ticks from birth were ranked for resistance to ticks by repeated whole-body counts of infesting ticks. Four cattle of high resistance, four of low resistance and two of intermediate resistance were artificially infested with nymphs of Amblyomma variegatum and Rhipicephalus appendiculatus. Two Friesian cattle (Bos taurus) with less exposure to ticks were similarly infested. Biopsies of tick attachment sites were examined histologically. All attachment sites showed acute inflammatory lesions, and sites of both tick species on high resistance cattle showed delayed hypersensitive reactions with intra-epidermal pustulation and significant increases in the numbers of granulocytes. The predominant cells infiltrating attachment sites on high resistance cattle were eosinophils with A. variegatum and neutrophils with R. appendiculatus. Such differences need to be taken into account in developing immunological tests for selecting cattle for resistance but there are sufficient common features of reactions to the two infesting tick species to justify dermal hypersensitivity tests.     

Rhipicephalus sanguineus (Ixodida, Ixodidae) as intermediate host of a canine neglected filarial species with dermal microfilariae

The life cycles of filarioids of dogs presenting dermal microfilariae have been little studied. Following the recent retrieval of dermal microfilariae identified as Cercopithifilaria sp. in a dog from Sicily (Italy), this study was designed to assess the role of the brown dog tick Rhipicephalus sanguineus as an intermediate host of this filarial species. An experimental tick infestation was performed on an infected dog using 300 nymphs of R. sanguineus. Engorged nymphs were collected and examined by both microscopic dissection and molecular analysis at five time points (i.e., the same day of tick detachment and 10, 20, 30 and 50 days post-detachment) to detect the presence and developmental stage of filariae in the ticks. A total of 270 engorged nymphs were collected from the dog and developing filarioid larvae detected in 10 (5%) out of 200 ticks dissected. Infective third-stage larvae were observed in 4 (2%) of the all dissected ticks, 30 days post-detachment. Twelve (6.6%) out of 181 samples molecularly tested were positive for Cercopithifilaria sp. This study demonstrates that nymphs of R. sanguineus feeding on a dog naturally infected by Cercopithifilaria sp. can ingest microfilariae, which develop up to the third infective stage thus suggesting that this tick species might act as an intermediate host of this little known canine filarioid.     

Isolate of Anaplasma marginale not transmitted by ticks

The tick-borne transmissibility of 2 isolates of Anaplasma marginale was compared. Dermacentor variabilis were exposed to A marginale as nymphs by feeding on 1 of 4 splenectomized calves during periods of ascending parasitemia (maximum 49% to 81% parasitized erythrocytes) induced by injection of a stabilate. Tick-borne transmission was attempted, using 26 to 224 adult ticks within 30 to 220 days after molting. Adult D variabilis did not transmit an Illinois isolate of A marginale in 7 tick-borne transmission experiments (P = 0.0047), including 2 experiments in which calves were inoculated IV with homogenates of adult ticks. In contrast, a Virginia isolate of A marginale was readily transmitted by the same tick colony. Thus, previously reported morphologic and immunologic differences among A marginale isolates may extend to tick-borne transmissibility. The Virginia and Illinois A marginale isolates had an inclusion appendage that was not a marker for tick transmissibility.     

Infectivity rate and transmission potential of Hyalomma anatolicum anatolicum ticks for Babesia equi infection

The infectivity rate of Babesia equi in the salivary glands of Hyalomma anatolicum anatolicum was assessed. The hungry nymphs were fed on a donkey experimentally infected with B. equi. The engorged dropped-off nymphs were collected at different levels of parasitaemia and kept in BOD incubator. After ecdysis, the hungry adults were prefed on rabbits for different time intervals, thereafter the salivary glands were dissected out and acini were examined after methyl green pyronin (MGP) staining. A total of 134 male and 139 female ticks were dissected out. Average infected acini per tick were found to be significantly higher (p<0.05) in male as compared to the female ticks. Further, maximum infected acini in both male and female ticks were found at 24h of prefeeding on rabbits and overall infected acini per tick increased with rise in parasitaemia. The release of infected ticks on susceptible donkeys resulted in development of clinical babesiosis.     

Transmission of a Trypanosoma sp. to cattle by the tick Hyalomma anatolicum anatolicum

Hyalomma anatolicum anatolicum engorged nymphs and flat adults were collected from two areas in northern Sudan. Various developing stages of Trypanosoma theileri-like flagellates were observed in the engorged nymphs, freshly moulted adults and mature adults partially engorged on rabbits. When these ticks were applied to two calves, one calf became infected with the trypanosome. The parasites were observed for one day in the enlarged lymph node nearest to the tick-feeding site 5 days after the tick application. Subsequently the trypanosomes were re-isolated in vitro from the infected calf. Inoculation of a ground-up tick supernatant suspension from the infected batch of ticks containing 10(4) trypanosomes into a calf did not produce a patent infection.     

Experimental infection of ponies with Borrelia burgdorferi by exposure to Ixodid ticks

Seven specific-pathogen-free (SPF) ponies, 1-5 years old, were exposed to Borrelia burgdorferi-infected adult ticks while being treated with dexamethasone over 5 consecutive days. One SPF pony (pony No. 178) was first exposed to laboratory-reared nymphs without B. burgdorferi infection and 3 weeks later was exposed to B. burgdorferi-infected adult ticks with concurrent dexamethasone treatment for 5 consecutive days. Four uninfected ponies treated with dexamethasone, exposed to laboratory-reared ticks without B. burgdorferi infection served as uninfected controls. Clinical signs, bacteriologic culture, polymerase chain reaction (PCR) for bacterial DNA, immunologic responses, and gross lesions and histopathologic changes were investigated during the experiment or at necropsy 9 months after tick exposure. In all of the seven challenged ponies, infection with B. burgdorferi was detected from monthly skin biopsies and various tissues at postmortem examination by culture and by PCR. However, pony No. 178 exposed to laboratory-reared nymphs (without B. burgdorferi infection) and challenged with B. burgdorferi-infected adult ticks 2 months later did not develop a B. burgdorferi infection. All of the infected ponies seroconverted. Control ponies and pony No. 178 were negative by culture, PCR, and serology. Except for skin lesions, we failed to induce any significant histopathologic changes in this study. This is the first report of successful tick-induced experimental infection in ponies by exposure to B. burgdorferi-infected ticks. This Lyme disease model will be very useful to evaluate efficacy of vaccines against the Lyme agent and the effect of antibiotic therapy on horses infected with B. burgdorferi.     

Infectivity of three Anaplasma marginale isolates for Dermacentor andersoni

Three isolates of Anaplasma marginale--Virginia (VAM), Illinois (IAM), and Florida (FAM)--were compared for infectivity for Dermacentor andersoni. The isolates were selected, in part, because of a tail-like appendage that has been demonstrated in the VAM and IAM, but not in the FAM. Ticks were exposed to the isolates as nymphs either naturally by feeding on a calf with anaplasmosis or artificially by percutaneous inoculation with infected bovine erythrocytes. They were examined for infectivity after molting to the adult stage by determining their capability to transmit the disease to susceptible calves and by demonstrating colonies in tick gut sections. Only those ticks exposed to the VAM proved to be infected with A marginale; ticks naturally exposed and those artificially infected with this isolate transmitted the disease to susceptible calves. Colonies of A marginale were observed only in gut tissues of ticks naturally infected with VAM. The IAM (appendage present) and FAM (appendage absent) could not be found in ticks exposed by either method, indicating that factors other than the presence of inclusion appendages may be involved in infection of ticks by A marginale.     

Acaricidal activity of kupetaba, a ground mixture of natural products, against Rhipicephalus appendiculatus

Eight substances were screened for the purpose of selecting a natural product as an acaricide for use within an integrated tick management system. One substance proved to be effective as an acaricide against all stages of Rhipicephalus appendiculatus and was named 'kupetaba'. It is a ground mixture of dried tobacco leaves (family Solanaceae) and a mineral called 'Magadi soda' which is mined around Lake Magadi in the Rift Valley province of Kenya. Investigation showed that kupetaba is commonly sold in local markets in East, West and Central Africa, where it is used for many purposes. The substance prevented the completion of all feeding phases of the tick, suppressed the oviposition capacity of the engorged ticks and drastically reduced the hatchability of the eggs. Larvae and nymphs were killed within 24 h of the application of the substance on calves' ears, while large numbers of adult ticks were also killed within 2-3 days of application during in vitro experiments. The suitability of the natural product as a local acaricide which resource-poor farmers in Africa can use to replace commercial acaricides within an integrated tick management system is discussed.     

Exposure of cattle immunized with different stocks of Theileria parva to buffalo-associated Theileria challenge on two game parks in Zimbabwe.

Eight cattle immunized with cattle-derived Theileria parva Boleni stabilate together with six susceptible controls were released in Dombawera Game Park on the Highveld of Zimbabwe. This coincided with Rhipicephalus appendiculatus nymphal activity. The cattle grazed together with African buffaloes (Syncerus caffer) and were not treated against tick infestation. The nymphal tick infestation was high, and seven of the eight immunized cattle and three of the controls had severe and fatal reactions. Subsequently, two stocks of Theileria parva to be tested for their immunizing abilities were prepared-one from adult ticks which were fed as nymphs on one of the sick control animals (Dom 268) and the other from adult ticks collected from pastures grazed by buffaloes (Bv-1). Two groups of cattle were immunized with either the Dom 268-derived strain (eight animals) or the Bv-1-derived strain (four animals). These together with three non-immunized controls, were released in Bally Vaughaun Game Park in the Highveld, where buffaloes are present, during the season of nymphal tick activity. A third group of five cattle, immunized with stabilate Bv-1, and three non-immunized controls were released at the same site during the season of adult tick activity. The nymphal and adult tick infestations of the cattle were large and more than 2000 nymphs and 1000 adult ticks were counted per animal. Cattle were treated with a pyrethroid pour-on preparation to control the tick infestation and screw-worm strike. The immunized cattle in the three groups survived the theileriosis challenge for a period of 18 months, but the non-immunized control cattle suffered a severe and fatal theileriosis 19-23 days after being placed on the pasture.     

The effects of bovine tick resistance on the susceptibility of Hyalomma anatolicum anatolicum to infection with Theileria annulata (Ankara)

Two Bos taurus calves were made resistant to tick infestation by exposing them to approximately 500 rabbit-reared nymphs of Hyalomma anatolicum anatolicum twice at a 2-week interval. These two calves, together with a tick-susceptible control calf, were inoculated with a stabilate of Theileria annulata (Ankara). Patent infection resulted in all three calves. Seven-hundred and fifty gerbil-reared nymphs were then applied on each of these calves as well as another tick-susceptible calf that was Theileria free. This infestation was carried out on Day 8 post-inoculation. Ticks that dropped on Day 13 post-inoculation were examined to note the development of T. annulata in them and the histological changes that occurred in the gut and salivary glands. During the second phase of feeding, the gut epithelia of the ticks from the tick-resistant calves were less active. There were no notable differences in the characteristics of the developmental stages of T. annulata between the ticks from the tick-resistant calves and those from the susceptible calf. However, ticks from one calf that acquired a higher level of tick resistance were significantly less susceptible to infection by T. annulata. Bovine tick resistance therefore compromises the vector capacity of H. a. anatolicum and this may be of epidemiological significance in the endemic areas of tropical theileriosis.     

The natural hosts of larvae and nymphs of Amblyomma tigrinum Koch, 1844 (Acari: Ixodidae)

The hosts of larvae and nymphs of Amblyomma tigrinum, a tick whose adults feed on wild and domestic Canidae in South America, are uncertain. A 17 months survey was carried out trapping wild vertebrates in north-western Córdoba, Argentina, to evaluate their parasitism with A. tigrinum subadults. Larvae and nymphs of this tick species were identified conventionally and by comparison of 16S rDNA sequences with GenBank deposited sequences. A total of 207 small and medium-sized rodents and 182 birds were captured and examined for ticks. Most ticks on birds were from ground forest feeding birds (BB) with a minimal contribution of birds feeding in open pastures. All ticks from rodents were obtained from representatives of the families Cricetidae (SR) and Caviidae (MR). Percent of larvae infestation was higher (P<0.01, Chi-square distribution) in BB (55.2%) and SR (46.4%) than in MR (17.4%) and the same trend was found for number of larvae on these hosts (test of Kruskal-Wallis). Caviidae (only representative Galea musteloides) rodents were extremely prone to be infested with nymphs of A. tigrinum (94.2%) followed by BB (50.6%) and SR (3.6%) (P<0.01) and the same tendency was found for number of nymphs (P<0.01). The index of aggregation for nymphs on MR was the lowest (0.409) followed by nymphs on BB (0.706) which may be a consequence of higher and homogenous exposure of G. musteloides to host-seeking nymphs. Several BB are food source for both larvae and nymphs of A. tigrinum while for rodents larvae were common only on SR (mainly on the Sigmodontinae Akodon dolores and Graomys sp.) and nymphs feed almost exclusively on MR. Therefore, both birds and rodents are of importance for the survival strategy of A. tigrinum subadults. The plasticity of A. tigrinum to colonize areas with different climates plus the capacity of their subadults to feed on hosts widely distributed indicates that this tick has the potential to become a widespread parasite but this does not seem to be the actual situation. Several proposals are presented to further understand its ecology.     

Ixodid ticks on indigenous goats owned by small-scale farmers in four communal grazing areas in South Africa

Indigenous goats belonging to small-scale farmers in 4 communal grazing areas in South Africa were sampled for ixodid ticks during the period September 1991 to May 1993. Three of these areas were in the North West Province (Rietgat, Madinyane and Bethany), and one in Mpumalanga Province (Geluk). No tick control was practised unless requested by the owners. Seven ixodid tick species, of which the majority were immature ticks, were collected from the goats in North West Province. Amblyomma hebraeum was the most numerous of these, followed by Rhipicephalus evertsi evertsi and Rhipicephalus appendiculatus. Substantially more ticks were collected from goats at Rietgat than at the Madinyane and Bethany grazing areas. Five tick species were collected at Geluk and R. evertsi evertsi comprised more than 95 % of the total population. At Rietgat and Geluk A. hebraeum nymphs were present on goats throughout the year, while most R appendiculatus nymphs were collected during September and October 1991 and most adults during January and February 1992. At both Rietgat and Geluk most immature R. evertsi evertsi were collected from spring to late summer, while adults were present throughout the year.     

A comparison of susceptibilities to infection of four species of Hyalomma ticks with Theileria annulata

In this comparative study unfed nymphs of four Hyalomma tick species (Hyalomma anatolicum anatolicum, Hyalomma anatolicum excavatum, Hyalomma detritum and Hyalomma marginatum marginatum) were allowed to engorge on calves experimentally infected with Theileria annulata. The infection prevalence in the salivary glands of the adult female and male ticks of each Hyalomma species used in the study were assessed. The infection prevalence with T. annulata was high and did not vary markedly in the four Hyalomma tick species. The mean number of infected acini per tick in female and male ticks was different with female ticks having higher numbers of infected acini than the male ticks. The sex difference was more significant between H.a. anatolicum and H.a. excavatum than between H. detritum and H.m. marginatum. This study clarifies the roles of four Hyalomma tick species, and their sex, in the development of T. annulata.     

Hosts, seasonality and geographic distribution of the South African tortoise tick, Amblyomma marmoreum

The tortoise tick Amblyomma marmoreum was collected from large numbers of reptiles and other animals during the course of numerous surveys conducted in South Africa. A total of 1229 ticks, of which 550 were adults, were recovered from 309 reptiles belonging to 13 species, with leopard tortoises, Geochelone pardalis being the most heavily infested. The 269 birds sampled harboured 4901 larvae, 217 nymphs and no adult ticks, and the prevalence of infestation was greatest on helmeted guineafowls, Numida meleagris. Only two larvae were recovered from 610 rodents, including 31 spring hares, Pedetes capensis, whereas 1144 other small mammals yielded 1835 immature ticks, of which 1655 were collected from 623 scrub hares, Lepus saxatilis. The 213 carnivores examined harboured 2459 ticks of which none were adult. A single adult tick and 6684 larvae and 62 nymphs were recovered from 656 large herbivores, and a total of 4081 immature ticks and three adults were collected from 1543 domestic animals and 194 humans. Adult male and female A. marmoreum were most numerous on reptiles during January and February, and larvae during March. The largest numbers of larvae were present on domestic cattle and helmeted guineafowls in the Eastern Cape Province during March or April respectively, whereas larvae were most numerous on helmeted guineafowls, scrub hares and the vegetation in north-eastern Mpumalanga Province during May. In both provinces nymphs were most numerous between October and December. Amblyomma marmoreum appears to be most prevalent in the western regions of the Western and Eastern Cape and Free State provinces, and the north-eastern regions of the Northern Cape, KwaZulu-Natal, Mpumulanga and Limpopo provinces.     

Saturation deficit and deer density affect questing activity and local abundance of Ixodes ricinus (Acari, Ixodidae) in Italy

The wood tick Ixodes ricinus, one of the most common arthropod-borne disease vectors, is of increasing relevance for human and animal health in Europe. The aim of this study was to determine the relative contribution of several abiotic and biotic factors potentially affecting questing activity and local abundance of I. ricinus in Italy, considering the scale at which these factors interact with the host-seeking ticks. Within EDEN, a large-scale EU collaborative project on eco-epidemiology of vector-borne diseases, we collected questing ticks for three consecutive years using a standard protocol at eleven sites in the Italian Alps and Apennines. A total of 25 447 I. ricinus were collected. All sites showed the same annual pattern of tick activity (bimodal for nymphs and unimodal for larvae and adults), although the abundance of nymphs was statistically different between sites and years. A Generalized Linear Mixed Model and a Linear Mixed Model fitted to data for nymphs, showed that while the principal variables affecting the local abundance of questing ticks were saturation deficit (an index combining temperature and relative humidity) and red deer density, the most important variable affecting questing nymph activity was saturation deficit. As for the timing of seasonal emergence, we confirmed that the threshold temperature at this latitude for larvae is 10°C (mean maximum) while that for nymphs is 8°C.     

Experiments on transmission of an unidentified Theileria sp. to small ruminants with Haemaphysalis qinghaiensis and Hyalomma anatolicum anatolicum

Experiments on the transmission of an unidentified Theileria sp. infective for small ruminants by Haemaphysalis qinghaiensis and Hyalomma anatolicum anatolicum were carried out. Three Theileria-free batches of adult, larvae, and nymphs of laboratory reared H. qinghaiensis and Hy. a. anatolicum ticks were infected by feeding them on sheep infected with Theileria sp. The Theileria sp. was originally isolated from adult ticks of H. qinghaiensis, by inoculation of blood stabilates or tick transmission. H. qinghaiensis has been shown to be capable of transmitting the Theileria sp. infective for small ruminants transstadially to sheep and goats. The nymphs developed from the larvae engorged on the sheep infected with the parasite transmitted the pathogen to splenectomized sheep with prepatent periods of 30, 31 days, respectively; but the subsequent adult ticks of H. qinghaiensis derived from the nymphs did not transmit the pathogen to sheep. However, adults developed from the nymphs engorged on the sheep infected with the parasite transmitted the pathogen to sheep with prepatent periods of 24-27 days. The larvae, nymphs and adult ticks derived from female H. qinghaiensis ticks engorged on infected sheep were not able to transmit the parasite transovarially. The same experiments were done with Hy. a. anatolicum, but examination for presence of piroplasma of Theileria sp. from all animals were negative, demonstrating that Hy. a. anatolicum could not transmit the organism to sheep or goats.