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PubMed2004

Babesiosis of cattle.

Tick fever or cattle fever (babesiosis) is economically the most important arthropod-borne disease of cattle worldwide with vast areas of Australia, Africa, South and Central America and the United States continuously under threat. Tick fever was the first disease for which transmission by an arthropod to a mammal was implicated at the turn of the twentieth century and is the first disease to be eradicated from a continent (North America). This review describes the biology of Babesia spp. in the host and the tick, the scale of the problem to the cattle industry, the various components of control programmes, epidemiology, pathogenesis, immunity, vaccination and future research. The emphasis is on Babesia bovis and Babesia bigemina.

Animals↗
PubMed2000

Vector-host interactions in disease transmission.

Tick-borne spirochetes include borreliae that cause Lyme disease and relapsing fever in humans. They survive in a triangle of parasitic interactions between the spirochete and its vertebrate host, the spirochete and its tick vector, and the host and the tick. Until recently, the significance of vector-host interactions in the transmission of arthropod-borne disease agents has been overlooked. However, there is now compelling evidence that the pharmacological activity of tick saliva can have a profound effect on pathogen transmission both from infected tick to uninfected host, and from infected host to uninfected tick. The salivary glands of ticks provide a pharmacopoeia of anti-inflammatory, anti-haemostatic and anti-immune molecules. These include bioactive proteins that control histamine, bind immunoglobulins, and inhibit the alternative complement cascade. The effect of these molecules is to provide a privileged site at the tick-host interface in which borreliae and other tick-borne pathogens are sheltered from the normal innate and acquired host immune mechanisms that combat infections. Understanding the key events at the tick vector-host interface, that promote spirochete infection and transmission, will provide a better understanding of the epidemiology and ecology of these important human pathogens.

Animals↗
PubMed2002

Ultrastructural study of the infection process of Rickettsia conorii in the salivary glands of the vector tick Rhipicephalus sanguineus.

This work was designed to study the infection process of Rickettsia conorii in the salivary glands of experimentally infected Rhipicephalus sanguineus ticks. One hundred six uninfected engorged nymphs were intracelomically inoculated with approximately 2 x 10(3) plaque-forming units of a rickettsial suspension. After the molt, unfed and fed adults were dissected, and the salivary glands were extracted and processed for transmission electron microscopy observation. Three different uninfected control groups were used for (1) evaluating the impact of the inoculation procedure, (2) establishing the feeding period of infected ticks, and (3) ultrastructural characterization of the salivary glands. Overall, 75.5% (80 of 106) of the nymphs inoculated with rickettsiae died during the molt or soon after hatching into adult instars; 50% (12 of 24) of the remaining infected adults showed severe malformations compromising their viability. In apparently healthy specimens, time of engorgement was longer. The contrast with the negative control groups was statistically significant, suggesting that R. conorii exerts a strong negative effect on the vector ticks. The ultrastructural study showed that in the salivary glands of infected ticks, rickettsial growth occurs preferentially in central, peripheral, and interstitial acini cells.

Animals↗
PubMed2006

Evaluation of E. ruminantium genes in DBA/2 mice as potential DNA vaccine candidates for control of heartwater.

Heartwater caused by the rickettsia Ehrlichia ruminantium (E. ruminantium) is an acute and fatal tick-borne disease of domestic and some wild ruminants. A user-friendly vaccine does not exist. We selected and tested nine genes of E. ruminantium for protection against challenge in a DBA/2 mouse model, in order to identify candidate genes for incorporation into a recombinant vaccine. Of the nine DNA vaccine constructs tested, four DNA constructs 14HWORF1/VR1012, 14HWORF2/VR1012, 27HWORF1/VR1012, and HSP58/VR1012 were not protective and were excluded from the study. The remaining five DNA constructs-MAP2/ VR1012, 1HWORF3/ VR1012, 4HWORF1/ VR1012, 18HWORF1/ VR1012, and 3GDORF3/ VR1012-offered partial protection against lethal challenge demonstrated by reduced mortalities compared to control groups. Protection was augmented when DNA primed mice were boosted with a respective homologous recombinant protein. Protection in these five groups was associated with the induction of cell-mediated or T helper 1 (Th1) type of immune responses characterized by the production of large amounts of interferon-gamma and interleukin-2 in in vitro proliferation assays using E. ruminantium antigens for stimulation. These responses were enhanced when the DNA-vaccinated DBA/2 mice were boosted with specific homologous recombinant protein vaccination. In a preliminary follow-up study, protection conferred by DNA vaccination with individual gene constructs was not enhanced when the protective constructs were administered in combination (including the map-1 gene of E. ruminantium). Further evaluation of these and other untested DNA constructs is necessary to optimize their expression in vivo in the presence of molecular adjuvants, such as the IFN-gamma gene, GM-CSF gene, IL-12 gene, and CpG motifs to fully evaluate their protective value.

Animals↗
PubMed2001

Transmission of hepatozoon canis to dogs by naturally-fed or percutaneously-injected Rhipicephalus sanguineus ticks.

Hepatozoon canis is an apicomplexan protozoan parasite of dogs, prevalent in Asia, Africa, and southern Europe. Experimental transmission of H. canis to dogs was performed with laboratory-reared Rhipicephalus sanguineus nymphs that fed on a naturally infected dog or were percutaneously injected with canine blood containing H. canis gamonts. Dogs were inoculated by oral ingestion of adult ticks containing H. canis oocysts. Transstadial transmission of H. canis was recorded, whereas transovarial transmission could not be demonstrated. Oocysts were detected in 85% of the adult ticks that had engorged as nymphs on an infected dog and in 61% of the adult ticks resulting from nymphs injected percutaneously with blood from the same dog. Nine of 12 dogs (75%) inoculated with naturally fed or percutaneously injected ticks became parasitologically positive, and all showed seroconversion. Meronts were initially detected in the bone marrow 13 days postinoculation and gamonts 28 days after infection. The variation in the time of initial detection of parasitemia among infected dogs and the rapid appearance of gamonts in dogs immunosuppressed with corticosteroids suggest that immune mechanisms play an important role in controlling H. canis parasitism. The artificial acquisition of Hepatozoon parasites by percutaneous injection of ticks, demonstrated here for the first time, may serve as a useful tool for studies on transmission, vector-host relationships, and the immunology of infection with Hepatozoon species.

Animals↗
PubMed1996

Prospects for subunit vaccines against tick-borne diseases.

Tick-borne parasites are a serious impediment to the improvement of live-stock production in the developing world. The major parasites affecting cattle include Theileria parva, T. annulata, Babesia bigemina, B. bovis, Anaplasma marginale and Cowdria ruminantium. The control of these infections is dependent on the use of acaricides to decrease transmission by the tick vectors, and immunization of susceptible animals with live vaccines. The use of acaricide is hampered by the development of resistance, and live vaccines require cold chain facilities, which are generally unreliable in developing countries. There is therefore a need for improved vaccines that can circumvent these problems. There is a subunit vaccine being developed for T. parva based on the major surface antigen of the sporozoite (p67). A similar antigen, SPAG 1, has been identified as a candidate for T. annulata. Although several candidate antigens have been identified for Babesia spp., progress towards development of a subunit vaccine based on these antigens has been hampered by polymorphism among isolates and between species, and lack of knowledge of the immune effector mechanisms responsible for protection. The search for protective antigens of A. marginale has focused on outer membrane proteins; immunization with a variety of these antigens alone or in combination, has yielded promising results. As with Babesia, further definition of immune effector mechanisms is needed to optimize immunization strategies. The work on identifying the protective antigens of C. ruminantium is in its embryonic stages; however, two antigens have been identified and are currently being evaluated. There is high expectancy for subunit vaccines for all these diseases; however there is need for further work to elucidate the immune mechanisms in order to select appropriate antigen delivery systems.

Anaplasma↗
PubMed1992

Questionnaire surveys of cases of tick bite and Lyme borreliosis in hunters in Hokkaido with reference to detection of anti-Borrelia burgdorferi antibody.

An epidemic of Lyme borreliosis on Hokkaido island, Japan, was surveyed by questionnaire in 587 hunters. The 308 returns (52.4%) revealed episodes of tick bite (usually 2 or more) in 210 cases. Skin rashes appeared in 164 cases. Associated itching, pain, etc., but not skin rash, were more frequent after 2 or more tick bite. Previous determinations of anti-Borrelia burgdorferi antibody titers in these subjects and in controls suggested an association with outdoor activities other than hunting, and among 33 cases of dermatological symptoms and 23 of articular symptoms, 4 and 2, respectively, were antibody-positive. Most of these antibody-positive subjects had suffered tick bite at least twice, but had had no antibiotic treatment. Three subjects with joint disorders were antibody-positive. These findings suggested that the many hunters exposed to Borrelia burgdorferi frequently carried latent infections, and that some had latent form of arthritis, dermatitis and other disorders.

Adult↗
PubMed1993

The epidemiology and control of camel dermatophilosis.

Camel dermatophilosis was only recently described. It appears however that it is more widespread than originally thought. In Kenya it has generally been found in the main semi-arid camel rearing areas of Samburu and Laikipia districts although it has not yet been found in the arid areas of Turkana district. In an investigation of ticks on 200 camels, no Amblyomma variegatum ticks were found although many other ticks were present. A. variegatum is suspected to transmit dermatophilosis in many domestic animals. The only control method of dermatophilosis currently practised in Kenya is in one commercial farm, where camels are regularly washed with a 1% potassium aluminium sulphate solution. The camels have shown progressive improvement. Recently, some 50 camels imported from Pakistan in this farm came down with a severe skin infection which closely resembled dermatophilosis. All imported adult camels were involved although no calves were involved. Since no bacteria were isolated from all the sick camels, it was thought to be due to vitamin deficiency.

Actinomycetales Infections↗
PubMed1990

Efficacy of ivermectin delivered from an intraruminal sustained-release bolus against natural infestations of five African tick species on cattle.

The efficacy of ivermectin delivered by an orally administered prototype sustained-release bolus over approximately 90 days was evaluated against natural infestations of five African tick species. Twenty cattle, allocated by restricted randomization based on counts of standard Boophilus decoloratus, were allocated to two groups and were either given an ivermectin bolus or designated as non-medicated controls. All cattle grazed a single pasture of native grasses for 20-40 days before treatment and until trial termination. Starting on Days 27, 40, 68 and 82 after bolus administration, four replicates were confined to individual tick-collection stanchions for 4 to 5-day periods. Ticks recovered from these cattle were counted by species, sex, and stage and degree of repletion; engorged females were weighed and incubated to determine the number which oviposited. For the other replicates, half-body counts of adult ticks (classified by species, sex and degree of repletion by females) were made at 1- and 2-week intervals through Day 90. Among replicates confined to stanchions periodically, fewer (P less than 0.05) engorged adult female B. decoloratus, Hyalomma spp., Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi were collected from bolus-treated cattle than from controls. Numbers of engorged adult female Amblyomma hebraeum were reduced, but differences were not statistically significant (P greater than 0.10). Among cattle maintained continuously on pasture, tick numbers were reduced on the ivermectin-treated groups. A significant (P less than 0.05) treatment by linear time effect was seen for all adult ticks counted except R. appendiculatus. A significant (P less than 0.05) treatment by quadratic time effect was seen for A. hebraeum, B. decoloratus and R. evertsi evertsi, and overall treatment differences were significantly different (P less than 0.05) for these species. The differences tended to increase with time. Except for Boophilus, reductions in tick numbers on treated animals relative to controls were not readily apparent. There were no adverse reactions attributable to ivermectin treatment or the presence of the bolus. Each treated animal retained its bolus throughout the trial, based on metal detection.

Administration, Oral↗
PubMed1989

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.

Animals↗
PubMed1991

Control of rickettsial diseases.

Prevention of rickettsial infections is aimed at individual control and epidemic measures (especially in epidemic typhus), vector and rodent control, milk pasteurization (in Q fever), chemoprophylaxis and immunoprophylaxis. In vector and rodent control, the main obstacle is the rise in resistance to insecticides and rodenticides. For this reason in vector control, apart from insecticides, enhancement of the natural immunity acquired by animals in response to tick infestation and vaccination with concealed tick antigens as well as the use of hormones, chemosterilants and genetic manipulation can also be considered. For short-term high-risk exposure, doxycycline may be an effective prophylaxis of illness but may not prevent infection with scrub typhus or spotted fever group rickettsiae. At present, for specific prevention by vaccination, only Q fever vaccines are available for common use. However, development of subunit vaccines, namely immunogenic rickettsial proteins, cloned and expressed in Escherichia coli, seems to be very promising.

Animals↗
PubMedDate not supplied

[Evaluation of cellular response in engorged females of Boophilus microplus (Canestrini, 1887) inoculated with Metarhizium anisopliae, Beauveria bassiana, Penicillium corylophilum or Fusarium oxysporum].

The effect of Beauveria bassiana, Metarhizium anisopliae, Penicillium corylophilum or Fusarium oxysporum on the dynamic of hemocytes presented in the haemolymph of engorged females of Boophilus microplus was studied. The inoculation was carried out with conidia suspension of different fungi in the concentration of 10(8) conidia/ml. A negative control group was inoculated with 0.1% Tween 80 water solution and a testimony group was comprised of non inoculated ticks. The haemolymph samples were collected in 24, 48 and 72 hours post-challenge. In all the studied periods, prohemocytes, plasmatocytes, granulocytes, spherulocytes and oenocytoids were observed in the specimens inoculated with fungus and also in the controls groups (negative and testimony). Prohemocytes, plasmatocytes and spherulocytes were the most cells in the haemolymph. The absence of hemocytes 72h post-challenging was observed prior to the death of the specimens inoculated with B. bassiana suggesting a failure in the cellular response. Hyphae and conidia growth was observed in the samples treated with entomopathogenic fungi (B. bassiana or M. anisopliae). The groups treated with non entomopathogenic fungi (P. corylophilum or F. oxysporum) did not shown significant differences in relation to the negative control and testimony groups.

Animals↗
PubMed2001

Prophylaxis with single-dose doxycycline for the prevention of Lyme disease after an Ixodes scapularis tick bite.

BACKGROUND: It is unclear whether antimicrobial treatment after an Ixodes scapularis tick bite will prevent Lyme disease. METHODS: In an area of New York where Lyme disease is hyperendemic we conducted a randomized, double-blind, placebo-controlled trial of treatment with a single 200-mg dose of doxycycline in 482 subjects who had removed attached I. scapularis ticks from their bodies within the previous 72 hours. At base line, three weeks, and six weeks, subjects were interviewed and examined, and serum antibody tests were performed, along with blood cultures for Borrelia burgdorferi. Entomologists confirmed the species of the ticks and classified them according to sex, stage, and degree of engorgement. RESULTS: Erythema migrans developed at the site of the tick bite in a significantly smaller proportion of the subjects in the doxycycline group than of those in the placebo group (1 of 235 subjects [0.4 percent] vs. 8 of 247 subjects [3.2 percent], P<0.04). The efficacy of treatment was 87 percent (95 percent confidence interval, 25 to 98 percent). Objective extracutaneous signs of Lyme disease did not develop in any subject, and there were no asymptomatic seroconversions. Treatment with doxycycline was associated with more frequent adverse effects (in 30.1 percent of subjects, as compared with 11.1 percent of those assigned to placebo; P<0.001), primarily nausea (15.4 percent vs. 2.6 percent) and vomiting (5.8 percent vs. 1.3 percent). Erythema migrans developed more frequently after untreated bites from nymphal ticks than after bites from adult female ticks (8 of 142 bites [5.6 percent] vs. 0 of 97 bites [0 percent], P=0.02) and particularly after bites from nymphal ticks that were at least partially engorged with blood (8 of 81 bites [9.9 percent], as compared with 0 of 59 bites from unfed, or flat, nymphal ticks [0 percent]; P=0.02). CONCLUSIONS: A single 200-mg dose of doxycycline given within 72 hours after an I. scapularis tick bite can prevent the development of Lyme disease.

Adolescent↗
PubMed1975

Study of rickettsioses in Slovakia. I. Coxiella burneti and Rickettsiae of the spotted fever (SF) group in ticks and serological surveys in animals and humans in certain selected localities in the Lucenec and V. Krtís districts.

A study of the natural focus character of Q fever and the rickettsiosis caused by organisms of the SF group carried out in 1971-1973 in 7 selected villages in the Lucenec district and in a few control villages in the V. Krtis district, produced the following results: Among a total number of 2,200 ticks belonging to the species Dermacentor marginatus, Ixodes ricinus and Haemaphysalis punctata and tested for the presence of rickettsial organisms by the haemocyte test, C. burneti was detected in 8 from the chosen localities--in 2 females and 1 male of D. marginatus in Luborec, in 1 2. ricinus female in Maskova and in 1 female and 3 males of I. ricinus in Pincina--and in 5 from the control localities--in 1 D. marginatus female in Prebelce and in 3 females and 1 male of D. marginatus in V. Lom.

Animals↗
PubMed1983

The efficacy of ivermectin against helminth and arthropod parasites of impala.

The efficacy of ivermectin, injected subcutaneously at a dosage rate of 200 mcg/kg live mass, was determined against nematodes, ixodid ticks and lice infestations acquired by free-living impala, Aepyceros melampus, in the Kruger National Park. Although the parasite burdens of the untreated control animals varied considerably, ivermectin appeared to be highly effective against 7 nematode species and effective against 3 others. Of the 4 tick species recovered, only Boophilus decoloratus appeared to have been affected. In the case of the lice infestations, ivermectin was highly effective against 3 species of Linognathus, but ineffective against the 2 Damalinia species present.

Animals↗
PubMed1979

Epidemiology and control of anaplasmosis in Australia.

Anaplasmosis occurs in those areas of northern and eastern Australia infested by the cattle tick Boophilus microplus but it has been studied intensively only in Queensland. Anaplasmosis is predominantly a disease of autumn and winter and of cattle greater than 1 year of age. The complement fixation test has been used in serological surveys of the tick-infested areas of the state. Both clinical and subclinical infections occur only in tick-infested areas and they are both more frequent in Bos taurus than in Bos indicus cattle probably due to the greater susceptibility of the former to ticks. Prevalence of infection is significantly greater in cattle exposed to heavy tick infestations than it is in cattle exposed to light tick infestations. B. microplus is considered to be the main vector with transmission being effected by transtadial and intrastadial but not transovarial means. Transtadial transmission by Rhipicephalus sanguineus has been demonstrated but attempts to demonstrate transmission by Haemaphysalis longicornis were unsuccessful. Vaccination with Anaplasma centrale is employed either as a routine preventative measure in young cattle or in the face of an outbreak. Attempts to attenuate a strain of A. marginale by adapting it to sheep were unsuccessful. Oxytetracycline and imidocarb have been used successfully to control the clinical disease.

Anaplasmosis↗
PubMed2005

Adaptive significance of avian beak morphology for ectoparasite control.

The beaks of Darwin's finches and other birds are among the best known examples of adaptive evolution. Beak morphology is usually interpreted in relation to its critical role in feeding. However, the beak also plays an important role in preening, which is the first line of defence against harmful ectoparasites such as feather lice, fleas, bugs, flies, ticks and feather mites. Here, we show a feature of the beak specifically adapted for ectoparasite control. Experimental trimming of the tiny (1-2 mm) maxillary overhang of rock pigeons (Columba livia) had no effect on feeding efficiency, yet triggered a dramatic increase in feather lice and the feather damage they cause. The overhang functions by generating a shearing force against the tip of the lower mandible, which moves forward remarkably quickly during preening, at up to 31 timesper second. This force damages parasite exoskeletons, significantly enhancing the efficiency of preening for parasite control. Overhangs longer than the natural mean of 1.6mm break significantly more often than short overhangs. Hence, stabilizing selection will favour overhangs of intermediate length. The adaptive radiation of beak morphology should be re-assessed with both feeding and preening in mind.

Adaptation, Biological↗