Sergio Da Silva

Relationships and influences between Boophilus microplus characteristics in tick-naive or repeatedly infested cattle

Six tick-naive male Hereford calves were infested once a month for 6 months with 18,000 Boophilus microplus larvae on the back and with 400 larvae in a cloth bag glued on the lumbar region. Working with the bag ticks, 12 tick characteristics were recorded for each infestation. Each tick attribute was analyzed for significant differences with those of the first infestation (analysis of variance), and for similarity (clustering), degree of relationship (correlation), and concomitant variation (regression) against all the other attributes during the first, third, and sixth infestations. Some attributes were affected maximally by host immunity about the third infestation but recovered later (length of feeding, detachment weight, egg weight, start of oviposition, fertility efficiency index), whereas others continued to be affected until the last infestation (length of oviposition, corpse weight, start of hatching, feeding efficiency index). All analyses showed that weight at detachment and egg weight were closely related, and corpse weight was partially related to these two. All other natural characteristics were largely independent. Length of feeding showed no significant relation with weight at detachment nor length of oviposition with egg weight. These findings suggest that different tick functions are independently affected by host immunity and recommends against estimating general anti-tick resistance by the evaluation of only a few tick characteristics.

Comparative IgG recognition of tick extracts by sera of experimentally infested bovines

Enzyme-linked immunosorbent assay (ELISA) and Western blot were used to investigate the pattern of antibody responses of six bovines infested twelve times with Rhipicephalus (Boophilus) microplus (Canestrini, 1887) (Acari: Ixodidae) (six heavy infestations followed by six light infestations) against salivary gland, gut and larvae extracts. During heavy infestations, bovine IgG levels were shown to be higher, and a decrease in the number and weight of ticks that completed the parasitic cycle was observed. The pattern changed starting from the seventh infestation, showing a decrease in IgG levels. An initial increase followed by a significant decrease in the proportion of ticks that completed the parasitic cycle was also observed from the seventh infestation. The number of molecules recognized by Western blot was higher from sera collected following heavy infestations than after light infestations, although a great variation in the profiles detected could be seen when the bovines were compared. These results indicate that IgG responses to different tick antigens may not be generally associated with bovine resistance, and that infestation levels modulate the magnitude of humoral responses and possibly the immune mechanisms in the natural acquisition of tick resistance.

Evaluation of a Frozen Trivalent Attenuated Vaccine against Babesiosis and Anaplasmosis in Brazila

Univ Estadual Londrina, Dept Vet Prevent Med, Ctr Ciencias Agrarias, BR-86051970 Londrina, Parana, Brazil

Presence of Gasterophilus (Leach, 1817) (Díptera: Oestridae) in horses in Rio Grande do Sul State, Brazil

ABSTRACT With the purpose of verify the presence of larvae from the genus Gasterophilus in the Rio Grandedo Sul State, a study was undertaken using 395 horses taken to slaughter in the city of Pelotas. Thematerial analysis revealed that 126 animals (31,90%) presented infection, with 100 animals (25,32%)infected by Gasterophilus nasalis , and 47 animals (11,90%) infected by G . intestinalis . These resultsalso represent the first report of the definite establishment of G. intestinalis as a horse parasite inBrazil. The probable implications of G. intestinalis occurrence in Brazil are discussed. Key words: Gasterophilus; G. nasalis; G. intestinalis. * Laboratorio de Doencas Parasitarias da Faculdade de Veterinaria, UFPel, Pelotas, Brasil.** Setor de Parasitologia, Departamento de Microbiologia, Instituto de Ciencias Basicas da Saude, UFRGS, PortoAlegre, Brasil. INTRODUCTIONThe genus Gasterophilus (Diptera, Oestridae)includes eight species of flies whose larvae causegastrointestinal myiasis in equids

Babesia bovis: infectivity of an attenuated strain of Brazilian origin for the tick vector, Boophilus microplus

In order to verify the infectivity and transovarian transmission of one strain of Babesia bovis of Brazilian origin, attenuated by repeated passages in splenectomized calves to the biological tick vector, Boophilus microplus, an inoculation of that strain was performed in hemoparasite-free calves infested with hemoparasite-free ticks. Subsequently, engorged female ticks were collected to examine hemolymph and progeny for presence of developing stages of Babesia bovis. Using an optical microscope, intrahemocytic merozoites were observed in female hemolymph on the second and fourth days, respectively, after ticks dropped from calves. By histological observation of F1 larvae, after more than 24 h of adherence on calves, sporokinetes and small merozoites were present in the samples of hemolymph. These results confirmed the maintenance of infectivity by the vaccine strain attenuated after 26 passages for tick Boophilus microplus.

Frequency of seropositive equines for Theileria equi in the Southern Rio Grande do Sul State, Brazil

ABSTRACT A study on equine theileriosis was carried out in the southern region of the Brazilian state of RioGrande do Sul (RS). Blood samples were collected from 113 mares from an equine breeding farmlocated in the city of Bage, latitude 31o30’ S and a longitude of 54U10’ W. The serological testing wascarried out with the use of indirect fluorescence test (IFAT) and compared with Nested PolimeraseChain Reaction (nPCR). Among the sera collected from 118 horses, 25 were found positive to Theileria equi by the IFAT, while by nPCR 17 positive for T. equi was observed, corresponding to afrequency of 22.1% and 15.0%, respectively. The racial analysis showed 15.05% (14) thoroughbredand 55% (11) Crioulo breed horses to be positive by IFAT. Key words: Theileria equi, IFAT, prevalence. INTRODUCTIONEquine piroplasmosis, caused by Theileriaequi and Babesia caballi , is considered to be themost important tick-borne disease of horse intropical and subtropical areas 1 . Clinicalmanifestation of the disease is variable includingfever, anemia, icterus, lethargy, and in somecases death

Alterações hematológicas e sorológicas em eqüinos experimentalmente infectados com Babesia equi

In the present study the haematological and serological changes showed by horses experimentally infected with B. equi, during different infection stages and after chemotherapy parasite sterilization, are reported. Ten horses clinically healthy and serologically negative for Babesia spp were inoculated with B. equi and treated with babesicidal drugs during ascending parasitemia. After the treatment the horses were separated in two groups: carriers, which developed the chronic babesial infection, and sterilized horses, which the parasites were eliminated. During the whole experiment, hematocrit, parasitemia and antibody titers were monitored to characterize its dinamics in the acute and chronical babesial infection, as well as after elimination of parasites.

Molecular characterization of the recombinant protein RmLTI-BmCG-LTB: Protective immunity against Rhipicephalus (Boophilus) microplus

The bovine tick Rhipicephalus (Boophilus) microplus is found in several tropical and subtropical regions of the world. This parasite transmits pathogens that cause disease, such as babesiosis (Babesia bovis and B. bigemina) and anaplasmosis (Anaplasma marginale). Tick infestations cause enormous livestock losses, and controlling tick infestations and the transmission of tick-borne diseases remains a challenge for the livestock industry. Because the currently available commercial vaccines offer only partial protection against R. (B.) microplus, there is a need for more efficient vaccines. Several recombinant antigens have been evaluated using different immunization strategies, and they show great promise. This work describes the construction and immunological characterization of a multi-antigen chimera composed of two R. (B.) microplus antigens (RmLTI and BmCG) and one Escherichia coli antigen (B subunit, LTB). The immunogenic regions of each antigen were selected and combined to encode a single polypeptide. The gene was cloned and expressed in E. coli. For all of the experiments, two groups (treated and control) of four Angus heifers (3–6 months old) were used. The inoculation was performed via intramuscular injection with 200 μg of purified recombinant chimeric protein and adjuvated. The chimeric protein was recognized by specific antibodies against each subunit and by sera from cattle inoculated with the chimera. Immunization of RmLTI-BmCG-LTB cattle reduced the number of adult female ticks by 6.29% and vaccination of cattle with the chimeric antigen provided 55.6% efficacy against R. (B.) microplus infestation. The results of this study indicate that the novel chimeric protein is a potential candidate for the future development of a more effective vaccine against R. (B.) microplus.