Influence of parasiticide treatment on kinetics of antigen specific antibody response in cattle infested with Hypoderma lineatum (Diptera:Oestridae).

The effect of parasiticide treatment on dynamics of antigen specific antibody responses to Hypoderma lineatum (De Villers) was investigated in naturally infested calves. Parasiticides were applied to cattle 1 month prior to, 1 week prior to, and coincident with the appearance of warbles in untreated calves from the same source herd. When cattle were treated approximately 1 month before warbles appeared in untreated control animals, antigen specific antibody levels increased for 25-34 days then declined to undetectable levels by approximately 75 days. Antigen specific antibody levels sharply declined in cattle treated 1 week prior to appearance of warbles in untreated controls. Treatment applied coincident with arrival of grubs on the back did not alter the antigen specific antibody profile, but reduced the relative magnitude of antigen specific antibodies present. Persistence of the antigen specific antibody following treatment will permit conduct of serological surveillance programmes.

Antibody immunoglobulin G (IgG) response to Alouattamyia baeri (Diptera:Cuterebridae) parasitism of howler monkeys, Alouatta palliata, in Panama.

Larval bot fly burdens and the presence of immunoglobulin G (IgG) antibodies to larval antigens of Alouattamyia baeri (Shannon & Greene) were determined in howler monkeys, Alouatta palliata authority, from Barro Colorado Island, Panama, during July and August of 1991 and 1992. Monkeys produced antibodies (IgG) to both 1st- and 3rd-instar proteins of the monkey bot as measured by an enzyme immunoassay. The response to 1st-instar antigen was correlated with number of bots for the 1991 data and for pooled data from 1991 and 1992. No correlation was observed for the response to 3rd instar antigen. First-instar extracts were composed of 9 major proteins as visualized by SDS-PAGE. Bands at 17, 25, and 32 kDa were positive in Western blots. Third-instar extracts contained at least 13 major bands, with those at 120 and 130 kDa reactive in immunoblots. The immune response to A. baeri may be involved in limiting larval bot numbers.

Antibody responses in cattle infested with Haematobia irritans irritans (Diptera: Muscidae).

Antibody response to feeding by the horn fly, Haematobia irritans irritans (L.), was measured in naturally infested cattle as well as in controlled infestations. Humoral antibody level was not correlated with fly abundance in natural infestations. Correlations between the antibody response and fly abundance were extremely variable among animals. Antibody response to horn fly salivary antigens peaked within 4 wk after fly abundance reached 150 flies per animal. In controlled infestations, antibody response was weak during an initial exposure to 200 flies per animal, but increased after flies were removed from the cattle. Horn fly salivary antigen may have an immunomodulatory effect on the host.

A model for estimating abundance of cattle grub (Diptera: Oestridae) from the proportion of uninfested cattle as determined by serology.

A model is presented for determining the abundance of cattle grubs in the backs of calves from the proportion of uninfested calves in a herd. The distribution of grubs in calves' backs was compared with the negative binomial, but no relationships were found among the distribution parameters, suggesting that the negative binomial is an inappropriate choice for the basis of a sampling model. The relationship between the mean number of grubs per animal (mean), variance (delta 2), and proportion of uninfested calves (p0) in a herd was determined and used as the basis for the sampling model. The relationship between p0 and p0e [determined using serology (ELISA)] was evaluated. The variance of estimates of mean grubs per animal based on the regression model and uncertainty due to using p0e as an estimate of p0 was examined. A test of the model indicated that p0e could be used to obtain a reliable estimate of mean grubs per animal and that the method would be applicable for monitoring grub populations, assessing chemical control programmes, and determining release rates of sterile insects for control.

Enhanced resistance to cattle grub infestation (Hypoderma lineatum de Vill.) in calves immunized with purified hypodermin A, B and C plus monophosphoryl lipid A (MPL).

The influence of an antigen-specific cellular and humoral immune response, stimulated by immunization, on survival of a challenge infestation of Hypoderma lineatum was investigated. Calves immunized with a purified combination of hypodermin A, B and C plus monophosphoryl lipid A (MPL) developed a strong antigen-specific cellular immune response by completion of the immunization schedule which persisted to 12 weeks post-infestation. Responsiveness of peripheral blood lymphocytes to the mitogens concanavalin A and pokeweed was also elevated at 4 and 12 weeks post-infestation. Western blot analysis at the time of maximum grub counts demonstrated that immunized calves responded to hypodermin A, B and C while those receiving only MPL or infested controls responded only to hypodermin B and C. The antigen-specific antibody response as measured by ELISA at maximum grub count was significantly higher in vaccinated calves than in infested controls while the response in calves receiving only immunostimulator was also significantly elevated. Immunized (antigen plus MPL) calves produced 5.0 +/- 6.9 grubs per animal which successfully pupated while those receiving MPL alone produced 16.4 +/- 6.1 and infested controls produced 32.2 +/- 10.9 grubs per animal.

Mammalian immune responses to myiasis.

Myiasis is responsible for significant losses to the livestock industry worldwide. Control programs have been successful in reducing the number of infested animals. However, serious concerns regarding the use of pesticides have prompted research into alternative strategies for pest control. In this article, Bob Baron and Doug Colwell discuss progress made towards the understanding of the immune response to Hypoderma spp and other myiasis-producing arthropods. Prospects for vaccination are discussed.

Cleavage of purified bovine complement component C3 in larval Hypoderma lineatum (Diptera: Oestridae) hypodermins.

Proteinases isolated from first instars of Hypoderma lineatum (Villers) were assayed for their ability to degrade purified bovine complement component C3. Cleavage products were analyzed by SDS-PAGE followed by immunoblotting. Crude extracts (raw insect homogenate) and purified hypodermin A and B were effective in degrading the alpha chain of C3 at a concentration of 1 microgram/ml. At 10 micrograms/ml, raw insect homogenate caused total degradation of both chains of the molecule, whereas 50 micrograms/ml of hypodermin A was required to obtain similar results. Hypodermin B did not appear to cleave the beta chain of C3. No degradation of the C3 molecule was observed in the absence of added hypodermins. Complement degradation associated with Hypoderma infestations may allow the parasite to escape host defense reactions.

Early detection of cattle grub (Hypoderma lineatum and H. bovis) (Diptera, Oestridae) using ELISA.

An enzyme-linked immunosorbent assay (ELISA) to detect cattle grub-infested animals in the autumn in Alberta has been developed. Antibody to Hypoderma lineatum de Vill. was detectable as early as 6 weeks post-infestation in artificially infested steers. Peak antibody concentrations preceded the peak in maximum 'apparent' grub numbers which occurred between 37 and 43 weeks after infestation. Natural infestations with H. lineatum and H. bovis L., ranging from one to ninety-two grubs per calf, were readily detected by November and the incidence of false positives in uninfested calves was only 5%. Low level (1-4 grubs) infestations of H. bovis only became detectable in February with peak antibody concentrations occurring at the end of April. Prevalence of cattle grub infestations in southern Alberta was shown to be 37% during this study.

Lymphocyte responsiveness in cattle previously infested and uninfested with Hypoderma lineatum (de Vill.) and H. bovis (L.) (Diptera: Oestridae).

Cattle exposed to their third consecutive warble (Hypoderma lineatum and H. bovis) infestation had significantly reduced apparent and accumulative grub populations and produced significantly fewer grubs than animals exposed to their first infestation. These resistant animals had enhanced reactivity to mitogens (concanavalin A (con A) and pokeweed) upon reinfestation and a strong antigen-specific response at 2 months post-infestation. Their responsiveness to con A and antigen was also enhanced at 7 months post-infestation when grubs appeared in the backs, and the response to antigen continued at 10 months post-infestation. Responsiveness to mitogens in previously uninfested animals was similar to the control response throughout the infestation apart from the suppression of the con A response at 7 months post-infestation. These animals finally responded to antigen at 10 months post-infestation. These results suggest that acquired resistance to hypodermosis has a cellular basis with participation of both B- and T-cell components.

Immunological responses to parasitic arthropods.

Parasitic arthropods are responsible for enormous economic losses to livestock producers throughout the world. These production losses may range from simple irritation caused by biting and non-biting flies to deaths and/or damage to carcass, fleece, or skin resulting from attack by myiasis flies. The estimated costs of these losses are colossal but even these usually include only direct losses and ignore those associated with pesticide application. In the USA alone (in 1976), these losses were conservatively estimated at more than 650 million US dollars. The long term use of chemical control measures for these pests has resulted in many serious problems including residues in meat and milk products, rapid development of insecticide resistance, the destruction of non-target organisms, environmental pollution, and mortality and morbidity of livestock. These concerns have prompted researchers to seek alternative methods of arthropod control, including the artificial induction of immunity. In this review, R. W. Baron and J. Weintraub discuss several examples of ectoparasites that can induce immunological resistance in the host, including Sarcoptes and Demodex mites, the sheep ked (Melophagus ovinus), Anopluran lice and myiasis-causing flies such as Hypoderma.

Immunization of cattle against hypodermatosis (Hypoderma lineatum (deVill.) and H. bovis (L.)) using H. lineatum antigens.

The feasibility of immunizing calves against Hypoderma lineatum and H. bovis with a crude H. lineatum larval extract or culture-derived antigen was investigated. Larval survival was followed through pupation. Grub appearance in the backs of both of the immunized groups was found to be 50% of that in the control groups. First appearance of H. bovis was significantly retarded in both immunized groups; however, H. lineatum was unaffected. Duration of H. bovis dropping was also shorter in animals receiving crude extract than in controls while duration of dropping of H. lineatum was not influenced by immunization. Survival of H. lineatum larvae to pupation was significantly reduced in animals immunized with crude larval extract, but not in those receiving culture-derived antigen. H. bovis survival was reduced by both treatments.