A comparison of the effect of two regimens of infestation on the development of resistance by cattle to the cattle tick, Boophilus microplus (Can.)

The development of resistance to Boophilus microplus by cattle was studied using sets of cattle twins, in stalls. One twin from each set received 3 infestations of 40,000 larvae and the other a continuous infestation of 1,000 larvae a day over the same period. Sets of twins were then challenged with 1,000 larvae a day for 40 days and 2 field infestations of 20,000 larvae. Correlations of ranking for resistance made at 40-day periods during daily infestations of 1,000 larval ticks or for corresponding intermittent infestations of 40,000 larvae were low until animals had received 120,000 larvae. Thereafter irrespective of method of infestation correlations of ranking were relatively high (r = 0.61-0.96) between periods of infestations or method of infestation including 2 field infestations. Fewer adult female ticks matured on the daily infested animals than on the intermittently infested animals during the treatment period, but animals developed a similar resistance level whether infested with either technique.     

Effects of cattle tick (Boophilus microplus) infestation on the bovine immune system

The immunosuppressive effect of experimental Boophilus microplus infestation on bovine peripheral blood lymphocytes (PBL) and on host antibody production to a protein antigen (ovalbumin) was examined. Boophilus microplus infestation caused a marginal decrease in the percentage of T lymphocytes in PBL, which was observed in both lightly (5000 larvae) and heavily (40,000 larvae) infested cattle, and began at the second infestation and continued until the end of the fourth infestation. The percentage of B lymphocytes in heavily tick-infested cattle was less than that in non-infested control cattle after the fourth infestation. The response of PBL from tick-infested cattle to phytohemagglutinin (PHA) was always less than that of tick-free cattle after the second infestation. No noteworthy differences were detected between the three stages of tick infestation, that is, 1 week before the peak of adult engorgement, the middle of the peak and 1 week after all ticks had dropped. Boophilus microplus saliva (100 microliters ml-1) suppressed 47% of the response of bovine PBL to PHA in vitro. This suppressive effect of saliva may contribute to the lower responsiveness of PBL from tick-infested cattle. Antibody production by tick-infested cattle was examined during the third and fourth heavy tick infestation. Tick-infested cattle showed a diminished response against ovalbumin after the second immunization. The immunosuppressive effects of tick infestation may play an important role in tick survival or in the transmission of tick-borne diseases in the field.     

Chemical modifications of striatal A2A adenosine receptors: a possible role for tyrosine at the ligand binding sites

An indirect immunofluorescence test (IIF) and an enzyme-linked immuno-sorbent assay (ELISA) were standardised to investigate the prevalence of bovine babesiosis caused by Babesia bigemina in experimentally and naturally infected bovids. Both IIF and ELISA detected antibodies to B. bigemina 7 days after experimental infection with 87.5% and 100% sensitivity, respectively. The IIF results indicated that a titre greater than 1:64 was a reliable indicator of B. bigemina infection. Serological study of 214 serum samples collected from Boophilus microplus infested cattle from the State of Orissa revealed 33.6% overall seroreactivity by ELISA, whereas IIF recorded 9.4%. Both IIF and ELISA showed some degree of cross-reactivity between Indian (Izatnagar) and Mexican strains of B. bigemina.     

Acaricidal efficacy of cypermethrine (a new synthetic pyrethroid) against Boophilus annulatus ticks in cattle

Resistance of ticks to acaricides had spread dramatically in recent years, so changing of acaricides periodically is needed to avoid resistant strains. Cypermethrine is a new pyrethroid acaricide recently introduced in the skin parasites control programs in Egypt. Fourteen crossbred cows (Friesian X Egyptian native) were used to assess the acaricidal efficacy of cypermethrine against Boophilus annulatus ticks. Cows were allocated into treated and control groups, each consists of 7 animals. At day 0 before treatment, ticks of more than 4.5 mm in length attached to both treated and control animals were counted and every week thereafter. The average tick number on vaccinated and control animals were counted and the efficacy percentage of cypermethrine was then determined. The number of ticks which laid eggs were counted in treated and control animals and hatching percentage of eggs were then calculated. Spraying of animals with cypermethrine showed that complete elimination of ticks occurred early on the 7th day post-treatment. The average number of ticks was 1673 and that of controls was 1578 at day 0 before treatment. The maximum efficacy (100%) was sustained for up to 7 weeks post-treatment after which the efficacy was slightly dropped and reached 98%. The results of cypermethrine on oviposition and egg hatchability of the ticks which survived treatment were surprising. The percentage of ticks collected from treated cows that succeeded to lay eggs was 22%, the average number of eggs laid per tick was 259 and hatching rate was 8.6%.     

The prevalence of ectoparasites in Ethiopian immigrants

Newly arrived Ethiopian immigrants in Israel were screened for ectoparasitic insects and mites. Of 304 individuals examined 65.1% were infested with the head louse (Pediculus humanus capitis). The infestation rate among children varied between 65 and 100%. Children aged 6-11 years were the most infested group and no differences between girls and boys were found. The infestation rate in children was significantly higher than that found in adults. Approximately 39% of those examined were infested with the body louse (Pediculus humanus humanus). The rate of infestation with this parasite was higher in adults than in children and higher in females than males. Ten percent of the immigrants examined were infested with the scabies mite (Sarcoptes scabiei) and 4.3% with the human flea (Pulex irritans).     

Factors affecting the detection of infestations of Boophilus microplus in tick control programs

Factors affecting the probability of detecting infestations of Boophilus microplus when herds of cattle are examined were studied. The probability of detecting a tick depends on the number of infested cattle in the herd, the probability of ticks being present on the areas of the beast examined, the efficiency of the examination and the proportion of the herd examined. A mathematical expression relating these factors was derived, and a range of values calculated to demonstrate the relative importance of each factor. It was evident that the efficiency of the examination should be kept better than 75%, and that it is necessary to employ a high sampling rate, preferably 100% of the herd. The probabilities of ticks being present on 6 predilection sites and 4 combinations of sites of an infested animal were determined experimentally. The tail butt, esutcheon, belly, dewlap and to a lesser degree neck and ear were all very suitable sites on which to find cattle ticks. A combination of tail butt, escutcheon and neck produced probabilities (0.58 and above) considered adequate to form the basis of an examination system. Examination systems used in New South Wales, Queensland, Argentina and at the United States-Mexico border are described. As a result of this study a new standardised system has been adopted by the Board of Tick Control for use by all New South Wales inspectors.     

Therapeutic and persistent efficacy of fipronil against Boophilus microplus (Acari: Ixodidae) on cattle

Cattle infested with all parasitic life-stages of Boophilus microplus (Canestrini) were treated once with a pour-on formulation of fipronil at 0.25, 0.5, or 1.0% active ingredient (AI) to determine the therapeutic efficacy. Additionally, cattle were infested at weekly intervals for 13 consecutive weeks after treatment to determine the persistent effectiveness of the three concentrations. Results of therapeutic efficacy of fipronil showed that with each increase in concentration there was a corresponding and often significant (P < 0.05) decrease in the numbers, fecundity and fertility of engorged females. The overall control of the Index of Reproduction (IR) achieved at 0.25 and 0.5% AI was 86.2 and 94.3%, respectively, while the control of the IR at the 1.0% AI concentration was 99.7%. The persistent efficacy of fipronil, like the therapeutic efficacy, was also dose related. The 0.25% AI treatment failed to provide complete protection (100%) against larval reinfestation, although control of the IR remained high (> 95%) for the first 6 weeks after treatment. In contrast, at 0.5% AI the control of the IR remained at 100% for the first 4 weeks after treatment, and was > 90% for an additional 2 weeks (6 weeks posttreatment). The 1.0% AI concentration afforded the longest residual activity, providing virtually 100% protection against larval reinfestation for 8 weeks after treatment was applied. Based on the results, neither the 0.25 or 0.5% AI concentration completely eliminated the immature stages of the tick (nymphs and larvae) on the host at the time of treatment (therapeutic efficacy), and the residual activity (persistent efficacy) did not prevent reinfestation by larvae for long periods after treatment. While the 1.0% AI concentration provided both therapeutic and residual efficacy that would be suitable for use in the eradication program, caution is still warranted because a few engorged females detached for up to 25 days after treatment, although none reproduced after the 6th day.     

Efficacy of amitraz (Taktic 12.5% EC) as a dip for the control of Boophilus microplus (Canestrini) (Acari: Ixodidae) on cattle

Four groups of cattle infested with Boophilus microplus (Canestrini) were each dipped in a different concentration of amitraz diluted from a 12.5% EC formulation to determine the efficacy and performance of the product in an 11,400 l dipping vat. Except for the period when heifers were dipped, animals were restrained in stanchions placed individually inside 3.3 x 3.3 m2 stalls within an open-sided barn. The amitraz in the vat was stabilized with hydrated lime to maintain a pH of ca. 12. Analyses of vat samples showed that concentrations of amitraz in the vat were 7.6 to 13% lower than the targeted concentrations of 0.010, 0.015, 0.020, and 0.025% active ingredient (AI) for dilutions prepared according to instructions on the manufacturer's label. The large quantity of hydrated lime added to the vat (10 kg/1000 l) interfered with the HPLC analysis of vat samples. Therapeutic efficacy of each of the four observed concentrations (0.0088, 0.0131, 0.0174, and 0.0231% AI) of amitraz was excellent (> 99% control). However, the rapid detachment of all ticks from an animal within a few hours after treatment with amitraz, that has been frequently observed, was not pronounced in the present study. Only 47% of the B. microplus detached in the first 4 h post-treatment, and 84% detached within the first 24 h. All of the treatments, except the lowest concentration, provided protection of cattle against re-infestation by B. microplus larvae for 14 days post-treatment. Possibly as a result of the formation of a compact layer of lime and amitraz on the bottom after the vat was undisturbed for six weeks, intense agitation was required to re-suspend the active ingredient.     

Immunization of bovines with an aspartic proteinase precursor isolated from Boophilus microplus eggs

The capacity of the Boophilus Yolk pro-Cathepsin (BYC) to induce a protective immune response in cattle against Boophilus microplus infestation was tested by vaccination experiments and by inoculation of monoclonal antibody (MAb) against BYC into fully engorged tick females. In immunization experiments the measurement of various biological parameters demonstrated a partial protection against B. microplus. A continuous decrease in the levels of specific antibodies was observed over 11 months when six bovines were maintained in field conditions. The inoculation of the MAb into tick females produced a dose-dependent decrease in oviposition and survival of the ectoparasite compared to the control.     

The 97 kDa linear IgA bullous dermatosis antigen is not expressed in a patient with generalized atrophic benign epidermolysis bullosa with a novel homozygous G258X mutation in COL17A1

Most populations and some species of ticks of the genera Boophilus (5 spp.) and Rhipicephalus (ca. 75 spp.) cannot be distinguished phenotypically. Moreover, there is doubt about the validity of species in these genera. I studied the entire second internal transcribed spacer (ITS 2) rRNA of 16 populations of rhipicephaline ticks to address these problems: Boophilus microplus from Australia, Kenya, South Africa and Brazil (4 populations); Boophilus decoloratus from Kenya; Rhipicephalus appendiculatus from Kenya, Zimbabwe and Zambia (7 populations); Rhipicephalus zambesiensis from Zimbabwe (3 populations); and Rhipicephalus evertsi from Kenya. Each of the 16 populations had a unique ITS 2, but most of the nucleotide variation occurred among species and genera. ITS 2 rRNA can be used to distinguish the populations and species of Boophilus and Rhipicephalus studied here. Little support was found for the hypothesis that B. microplus from Australia and South Africa are different species. ITS 2 appears useful for phylogenetic inference in the Rhipicephalinae because in genetic distance, maximum likelihood, and maximum parsimony analyses, most branches leading to species had >95% bootstrap support. Rhipicephalus appendiculatus and R. zambeziensis are closely related, yet their ITS 2 sequences could be distinguished unambiguously. This lends weight to a previous proposal that Rhipicephcalus sanguineus and Rhipicephalus turanicus, and Rhipicephalus pumilio and Rhipicephalus camicasi, respectively, are conspecific, because each of these pairs of species had identical sequences for ca. 250 bp of ITS 2 rRNA.     

Performance of abamectin bait formulations against German cockroaches (Dictyoptera: Blattellidae)

Commercial and experimental formulations of abamectin-based baits were evaluated in laboratory and field studies against the German cockroach, Blattella germanica (L.). In continuous exposure tests with adult males, toxicity and presumably bait consumption varied with the design of the bioassay. LT50s ranged from approximately 0.9 to > 41 d for an aerosol gel formulation for males deprived of water for 72 h before the test and for undeprived males tested with alternative food and water, respectively. Dry formulations had lower LT50s than water containing formulations for nondeprived males. There was no difference in bait toxicity between males deprived of food or water, but in arena tests, moist formulations were preferred by mixed-stage populations of cockroaches. Powder formulations were more repellent (approximately 14.9%) than moist formulations (approximately 6.4%) in Ebeling choice boxes assays, but all abamectin formulations had positive performance indices. A powder formulation reduced cockroach trap catch in infested apartments more rapidly when applied to 50, rather than 12 sites, even when the same amount of bait was applied per apartment. When applied at approximately 50 sites as a series of thin smears, an aerosol formulation provided nearly an 80% reduction in trap catch. Other abamectin formulations provided substantial, but smaller reductions in trap catch. Abamectin-based baits can reduce German cockroach populations when properly applied.     

Contact chemostimuli in the mating behaviour of the cattle tick, Boophilus microplus

Mating of the cattle tick Boophilus microplus is mediated by chemical stimuli on the cuticle of females. Males are arrested on the dorsum of females attached to the host, frequently sample the substrate, and then tip-over to the ventrally located gonopore. These behaviours are also observed in vitro when males are placed on a small glass bead treated with a female extract. Time spent and tip-over by male ticks on dummies is used in an assay to test the behavioural significance of fractions of the extract. TLC separation yields one apolar fraction that arrests males, though much less so than the whole extract, but lost tip-over behaviour. This apolar fraction contains a series of cholesteryl esters that, when tested individually, show no arrestment activity at levels present in the extract but, when combined, are as active as the fraction. When a small silica column is used for fractionation, all biological activity is reproduced after recombining the fractions. In addition to the early eluting apolar fraction containing cholesteryl esters, a set of highly active more polar fractions is isolated. Electrophysiological recordings from gustatory sensilla on the pedipalps of male B. microplus, which are regularly brought into contact with the cuticle of the female during mating, provide evidence for receptors in two of them responding to the whole extract and to the behaviourally active polar fractions. Mating behaviour involving arrestment and tip-over is clearly initiated by a mixture of chemical stimuli, and tip-over behaviour is associated with the more polar material.     

Aniline metabolism in two species of Arachnida: water-soluble metabolites

1. The metabolism of [14C]aniline in the cattle tick, Boophilus microplus (Canestrini) at 40 and 300 mug per animal) and in the spider, Nephila plumipes (at 40 mug per 100 mg) were studied. 2. In both species hydroxylation occurred yielding both free and conjugated o-and p-aminophenols. 3. The water-soluble metabolites affording aniline on acid hydrolysis were examined, and gamma-glutamylanilide (23% of dose) was identified as a tick metabolite (40 mug dose). This metabolite was not found in extracts of dosed spiders.     

Pruritus and dermal response to insect antigens in sheep infested with Bovicola ovis

This study examined the relationships among louse density, pruritus and dermal response to insect antigens in sheep infested with Bovicola ovis. Polypay and Columbia ewes were allocated to two groups, infested and naive, and louse densities and pruritus were monitored for 15 months. Ten months after the initial infestation, all sheep were tested for hypersensitivity on the midside and ears by intradermal injection of soluble extracts of B. ovis, Stomoxys calcitrans and Musca autumnalis. The areas of skin reactions were measured at 20 min, 1, 3 and 24 h after injection and skin thickness was measured at 24 h. Louse densities on Polypays were approximately 10 times greater than on Columbias, and pruritus was correlated with louse numbers at most inspections. Most pruritic behaviour was directed to the sides of infested sheep. Wheal and flare reactions developed rapidly to all extracts in both infested and naive ewes. Reactions to louse extract were larger in infested than naive sheep at all four times after injection. In the infested Polypays, reactions to louse extract were greater than to the fly extracts, but in naive sheep there was little difference among extracts. Reactions in naive Columbias were larger than in naive Polypays at 20 min, 1 and 3 h, but had almost completely abated in both groups at 24 h. Reactions in infested Columbias were greater than in infested Polypays at 20 min, but at 24 h reactions in the Polypays were larger. Louse numbers and pruritus were correlated with wheal areas and skin thickness at 24 h, but there was little relationship with the size of reactions at earlier times. These findings are consistent with the development of a hypersensitive response to B. ovis and suggest that dermal reactions to lice may influence sheep susceptibility.     

Boophilus microplus: passive transfer of resistance in cattle

Plasma from cattle highly resistant to the tick Boophilus microplus conferred some resistance to unexposed calves. In contrast plasma from hosts of low resistance had no significant effect compared with plasma from unexposed donors.     

Effects of the sucking louse (Linognathus vituli) on the grooming behaviour of housed calves

The behaviour of cattle with and without louse infestation was studied for eight weeks. Thirty-two crossbred calves were housed in groups of four at 20 weeks old. Sixteen of the calves were artificially infested with the long-nosed cattle louse Linognathus vituli and 16 were left uninfested as controls. In infested animals the number of lice on the shoulders averaged 2.3 per 10 cm length of parted hair. The recorded frequency of irritation, manifested by rubbing and self-licking, was significantly greater in the louse-infested calves than in the uninfested controls. The infested calves spent 28 s/h rubbing and 95 s/h self-licking, compared with 8 s and 62 s/h spent by the uninfested controls. The infested calves also spent more than twice as long scratching as the controls. There were no significant effects of the infestation on social grooming.     

A randomized, double-blind, placebo-controlled, crossover study to assess the immediate effect of sublingual glyceryl trinitrate on the ankle brachial pressure index, claudication, and maximum walking distance of patients with intermittent claudication

The conventional method of identifying acaricide resistance in a suspect tick population by the United Nations Food and Agriculture Organization packet assay is a laborious and time-consuming process. DNA probes have been demonstrated as rapid and accurate tools for detecting pesticide resistance in insect species. Random-amplified polymorphic DNA (RAPD) has been used by other groups to differentiate species of mosquitoes and populations within a mosquito species. By using different arbitrary oligonucleotides as primers with RAPD, we have demonstrated that various strains of Boophilus microplus (Canestrini) show different patterns of DNA fragments on agarose gel electrophoresis. The unique DNA fragments may be useful for developing probes that can detect acaricide resistance in field pest populations.     

Ctenocephalides felis flea infestation in horses

The horses were in two stables: in the first stable they were kept together with sheep and in the second stable they were kept together with goats. All horses in both stables were diagnosed as being infested with the cat flea Ctenocephalides felis felis. Foals were severely infested, whereas adult horses were only moderately infested.     

Clinical, clinico-pathological and serological studies of Babesia ovis in experimentally infected sheep

Clinical, clinico-pathological and serological studies were performed in sheep experimentally infected with Babesia ovis. Acute babesiosis occurred in all the lambs infested with adult Rhipicephalus bursa ticks and in one lamb infested with the larvae. The rate of parasitaemia and the degree of anaemia were not correlated. Decrease in the packed-cell volume ranged from 30 to 40%. Parasitized erythrocytes were not observed to block capillaries in the brain, which explained the absence of nervous symptoms in acute babesiosis. The kidneys were the most severely affected organs, exhibiting acute glomerulonephritis. The lesions observed were suggestive of vascular alteration and vascular stasis, leading to anoxia of the tissues. A disseminated intravascular coagulation (DIC) syndrome was recorded in sheep infected with babesiosis. A marked increase in the enzymes of the transaminase groups, mainly aspartate aminotransferase (AST), was observed. Enzymatic changes (increases in AST, alanine aminotransferase (ALT) and lactic dehydrogenase (LDH) and decreases in sorbitol dehydrogenase (SDH), alkaline phosphatase (ALP) and malic enzyme (MEZ)), decreases in total proteins and albumin, and increases in urea and creatinine might reflect the degree of severity of the damage to the liver and kidney tissues. Most of the lambs (85%) that were infested with larvae, and all lambs infested with adult R. bursa ticks, reacted serologically to B. ovis antigen. The serological reactions following infestation with the larvae occurred much later than those following infestation with the adult stage. The lambs which were infested with larvae showed mild clinical reactions when challenged by infected R. bursa adults, as compared with the reactions to the challenge in naive control animals. The serological findings, in addition to the fact that one splenectomized lamb reacted to larval infestation with acute ovine babesiosis, show that the preimaginal stages of R. bursa can transmit B. ovis, usually causing a sub-clinical disease. It is suggested that infections derived from preimaginal ticks in the winter can preimmunize sheep for the subsequent more severe infections derived from adult ticks in the summer. Furthermore, in the absence of a reliable vaccine against B. ovis, grazing flocks in the enzootic regions should be exposed to the preimaginal stages during their activity period (October-February) before exposure to the adult ticks in spring and summer (April-July).     

Prejunctional effects of cromakalim, nicorandil and pinacidil on noradrenergic transmission in rat isolated mesenteric artery

Quil A used with Boophilus microplus gut membrane antigen (GM) had a significant effect on antibody levels induced in sheep (P < 0.05) since GM alone did not induce a significant level of antibodies. Injection of a vaccine containing GM and Quil A, either subcutaneously or intramuscularly, induced similar levels of antibodies in sheep. However, Quil A injected subcutaneously induced acute inflammatory reaction. The amount of Quil A for use with GM was determined to be 1000 micrograms/ml. Immunostimulating complexes (ISCOMs) incorporating detergent-solubilized membrane midgut antigens (TX-GM) failed to induce an immune response in cattle without the addition of Quil A. The addition of Quil A to the ISCOMs containing TX-GM did not stimulate antibody responses greater than those stimulated by TX-GM plus Quil A, and protection in vaccinated cattle was 86% and 74%, respectively.