Gustavo Cauduro Cadore

Eficiência in vitro de acaricidas sobre carrapatos de bovinos no Estado do Rio Grande do Sul, Brasil

Infestation by ticks is responsible for significant economic losses to the cattle industry in several regions, including Rio Grande do Sul (RS) state. Losses may be derived from animal stress, weight loss and skin damage, as well as from costs with treatment. The indiscriminated use of pesticides against these parasites has resulted in high levels of genetic resistance to several drugs, representing a problem for disease control. Thus, the objective of this research was to evaluate the susceptibility of field specimens of Rhipcephalus (Boophilus) microplus to the acaricides used in the control of the parasite. Female ticks obtained from 42 farms in different counties of RS were submitted to the engorgeted female immersion test, to estimate the resistance of the parasite to the drugs. Amitraz in combination with chlorpyriphos was the most efficient drug, acting effectively in ticks from 100% of the tested farms (11/11). Associations of cypermethrin-chlorpyriphos-citronelol were efficient in ticks from 61% of the farms (25/41) and cypermethrin-ethion in 37% (10/27). Cypermethrin alone was efficient in 20,7% (6/29) and Amitraz. one of the most used products, was efficient in ticks from only 14,2% (6/42) of the farms. These results demonstrate that most drugs used in the control of R. B. microplus in the state present low efficacy, as measured by in vitro tests. The low drug efficacy is probably derived from the genetic resistance developed by the parasites due to the indiscriminated and inadequate use of these acaricides in the field.

Neosporose equina: ocorrência de anticorpos anti-Neospora spp. e associação entre status sorológico de éguas e de suas crias

Neospora caninum and N. hughesi are protozoa which can infect horses and can cause reproductive and neurological diseases, respectively. The pathogenesis of neosporosis in horses is poorly understood, as well as the sources of horizontal infection of N. hughesi. Furthermore, there are doubts about the role of the vertical transmission of Neospora spp. in maintenance of these parasites in equine populations. In this study, we evaluated: (1) the occurrence of infections by Neospora spp. in a population of mares (in reproductive age) on a farm of Crioula breed horses; and (2) the possible association between the serological status of mares and of their offspring, aiming to investigate, indirectly, the relevance of transplacental transmission for the occurrence of Neospora spp. in these horses. We found a highly significant association between the serological status of mares and their offspring. Although had been exposed to the same environmental risk factors, the descendants of seropositive mares had a higher percentage of seropositivity against Neospora spp. compared to the descendants of seronegative mares. The association between kinship and serological status indicates an influence of vertical (transplacental) infection raising the occurrence of Neospora spp. in the studied equine population.

Occurrence of antibodies anti-Neospora spp. in cart horses and Crioula breed horses from Rio Grande do Sul state

O objetivo deste estudo foi avaliar a frequencia de deteccao de anticorpos contra Neospora spp. em cavalos de carroca e em cavalos da raca Crioula. Para tal, 214 amostras de soro foram coletadas e analisadas pela tecnica de imunofluorescencia indireta, das quais 91 eram de cavalos de carroca e 123 de cavalos da raca Crioula, todas provenientes da regiao central do Rio Grande do Sul. As frequencias de anticorpos detectadas foram: 15,9% (34/214) na populacao total estudada, 15,4% (14/91) nos cavalos de carroca e 16,3% (20/123) nos cavalos da raca Crioula. Estes resultados sugerem que a infeccao por Neospora spp. esta presente igualmente nas duas populac oes. Assim, devido a importância e ao padrao da patogenese da neosporose em equinos, Neospora spp. deve ser incluido no diagnostico de problemas reprodutivos em eguas e em casos de problemas neurologicos em equinos.

Canine cutaneous neosporosis in Brazil

The clinical signs of infection in dogs with Neospora caninum are usually associated with neurological disorders and are seen in young dogs. In this brief case report we observed multifocal ulcerative and exudative skin nodules on the neck and pelvic limbs of a 10-year-old cocker spaniel dog. Infection with N. caninum was diagnosed on the basis of cytology and examination of skin tissues by PCR. The dog initially responded to treatment with clindamycin and then relapsed; the dog died. Infection with N. caninum may have been due in part to immune suppression due to hyperadrenocorticism; which either allowed for the development of a primary infection or reactivation of a latent infection by N. caninum with the occurrence of skin lesions.

In vitro evaluation of acaricides efficiency to bovine's ticks of Rio Grande do Sul State, Brazil

Infestation by ticks is responsible for significant economic losses to the cattle industry in several regions, including Rio Grande do Sul (RS) state. Losses may be derived from animal stress, weight loss and skin damage, as well as from costs with treatment. The indiscriminated use of pesticides against these parasites has resulted in high levels of genetic resistance to several drugs, representing a problem for disease control. Thus, the objective of this research was to evaluate the susceptibility of field specimens of Rhipcephalus (Boophilus) microplus to the acaricides used in the control of the parasite. Female ticks obtained from 42 farms in different counties of RS were submitted to the engorgeted female immersion test, to estimate the resistance of the parasite to the drugs. Amitraz in combination with chlorpyriphos was the most efficient drug, acting effectively in ticks from 100% of the tested farms (11/11). Associations of cypermethrin-chlorpyriphos-citronelol were efficient in ticks from 61% of the farms (25/41) and cypermethrin-ethion in 37% (10/27). Cypermethrin alone was efficient in 20,7% (6/29) and Amitraz. one of the most used products, was efficient in ticks from only 14,2% (6/42) of the farms. These results demonstrate that most drugs used in the control of R. B. microplus in the state present low efficacy, as measured by in vitro tests. The low drug efficacy is probably derived from the genetic resistance developed by the parasites due to the indiscriminated and inadequate use of these acaricides in the field.

A thymidine kinase-deleted bovine herpesvirus 5 establishes latent infection but reactivates poorly in a sheep model

The ability of thymidine kinase (tk)-deleted recombinant bovine herpesvirus 5 (BoHV-5tkΔ) to establish and reactivate latent infection was investigated in lambs. During acute infection, the recombinant virus replicated moderately in the nasal mucosa, yet to lower titers than the parental strain. At day 40 post-infection (pi), latent viral DNA was detected in trigeminal ganglia (TG) of all lambs in both groups. However, the amount of recombinant viral DNA in TGs was lower (9.7-fold less) than that of the parental virus as determined by quantitative real time PCR. Thus, tk deletion had no apparent effect on the frequency of latent infection but reduced colonization of TG. Upon dexamethasone (Dx) administration at day 40 pi, lambs inoculated with parental virus shed infectious virus in nasal secretions, contrasting with lack of infectivity in secretions of lambs inoculated with the recombinant virus. Nevertheless, some nasal swabs from the recombinant virus group were positive for viral DNA by PCR, indicating low levels of reactivation. Thus, BoHV-5 TK activity is not required for establishment of latency, but seems critical for efficient virus reactivation upon Dx treatment.

Reativação e distribuição do DNA latente do herpesvírus bovino tipo 5 no encéfalo de ovinos infectados experimentalmente

The biology of latent infection by bovine herpesvirus type 5 (BoHV-5) has been studied in cattle and rabbits, yet many aspects remain poorly understood. We herein investigated the suitability of lambs to investigate aspects of BoHV-5 latency. Thirteen six-month-old lambs inoculated intranasally (IN) with BoHV-5 strain SV-507/99 (titer of 106.8 TCID50/ mL) shed the virus in nasal secretions in titers up 105.5 TCID50/mL, during up to 11 days, developing virus neutralizing (VN) titers of 16 to 128 at day 30 post-inoculation (pi). The inoculated animals developed only a mild serous nasal secretion and transient hyperthermia. Examination of brain sections of five lambs euthanized at day 30 pi by PCR revealed the presence of latent DNA in the trigeminal ganglia (TG, 5 out of five), olfactory bulbs (OB, 5/5), pons (2/5), cerebellum (2/5) and cerebral cortex (1/5). Administration of dexamethasone (Dx, n=4) or flumethasone (FluM, n=4) to eight latently infected lambs at day 65 pi resulted in virus reactivation and shedding by 3 out of 4 individuals in each group. Virus shedding in nasal secretions started at day 3 post-treatment and lasted up to five days (1-5) in Dx treated lambs (titers up to 102.8TCID50/mL), was delayed and lasted up to three days (1-3) in FluM-treated lambs (titers up to 102.1 TCID50/mL). PCR examination of the brains of animals submitted to reactivation, at day 30 post-treatment, showed a pattern of distribution of latent viral DNA fairly similar to that found in those not submitted to reactivation. In summary, the ability of BoHV-5 to establish latent infection, the consistent colonization of TGs and OBs by latent viral DNA and virus reactivation induced by corticosteroid treatment are promising findings towards the use of lambs to study selected aspects of BoHV-5 latency.

Anticorpos anti-Neospora caninum em bovinos de leite do sudoeste do estado do Paraná

Since November 2007 until May 2009, 1,778 serum samples of cattle from dairy herds of the Southwest of Parana State, Brazil, were used for search of anti-Neospora caninum antibodies. The frequency of seropositive animals, assessed by IFAT, was 24.2% (431/1,178), showing a relatively high occurrence in the studied population. These results show that Neospora caninum is widely distributed in the dairy cattle in the Southwest of Parana State. The presence of Neospora caninum in a herd is worrisome, since this protozoan is closely related with reproductive disorders and low milk production in cattle.

Suscetibilidade de linhagens celulares e cultivos primários ao Neospora caninum

Neospora caninum is a protozoan of wide distribution and great importance to the cattle industry, mainly due to its associated reproductive losses. Cultured cells are widely used for isolation and multiplication of the agent in vitro with several purposes. Thus, this study aimed to evaluate the susceptibility of different cell cultures to infection by N. caninum. Among the cell cultures tested, four presented good susceptibility to the agent: cell lines VERO (yield of 21.2 taquizoites/cell) and MA-104 (17.1); primary bovine testicle (16.3) and lung cells (13.6). Primary bovine kidney (8.2 taquizoites/cell), MDBK (5.1) and RK-13 cell lines (0.4) presented moderate to low sensitivity. No viable taquizoites were detected in the culture of MDCK cells. These results demonstrate that MA-104 cells present adequate susceptibility to N. caninum compared to VERO cells, which have been largely used to multiply the parasite in vitro. Together with its easy manipulation, fast multiplication and relatively low nutritional requirements, these results indicate that MA-104 cells are adequate for multiplication of N. caninum in vitro.

Intra-uterine exposure of horses to Sarcocystis spp. antigens

The aim of this study was to examine the intra-uterine exposure to Sarcocystis spp. antigens, determining the number of foals with detectable concentrations of antibodies against these agents in the serum, before colostrum ingestion and collect data about exposure of horses to the parasite. Serum samples were collected from 195 thoroughbred mares and their newborns in two farms from southern Brazil. Parasite specific antibody responses to Sarcocystis antigens were detected using the indirect immunofluorescent antibody test (IFAT) and immunoblot analysis. In 84.1% (159/189) of the pregnant mares and in 7.4% (14/189) of foals we detected antibodies anti-Sarcocystis spp. by IFAT. All samples seropositive from foals were also positive in their respective mares. Serum samples of seropositive foals by IFAT, showed no reactivity on the immunoblot, having as antigens S. neurona merozoites. In conclusion, the intra-uterine exposure to Sarcocystis spp. antigens in horses was demonstrated, with occurrence not only in mares, but also in their foals, before colostrum ingestion these occurrences were reduced.