Seroprevalence and risk factors for Neospora caninum infection in cattle from the eastern Antioquia, Colombia.

Bovine neosporosis is a parasitic disease with worldwide distribution that causes important economic losses. Because of the limited information on the occurrence of Neospora caninum infection in Colombia, this study aimed to determine the seroprevalence and identify the risk factors associated with this infection in cattle in Antioquia, which is the largest milk-producing state in the country. We collected 1,038 blood samples from Holstein, Jersey and crossbred cows from 31 farms. An epidemiologic questionnaire was given to all the owners. A commercial ELISA kit was used as the diagnostic technique. The occurrence of anti-N. caninum antibodies was determined to be 28.3% (294/1038), and 100% of the screened farms were positive, indicating that all the properties had at least one positive animal. The seropositivity within each farm ranged from 5.5% to 50%. A multivariable logistic regression model identified the following as significant risk factors: history of abortion (OR = 5.33, p < 0.001), replacement with cattle purchased outside the farm (OR = 1.54, p < 0.05), age (OR = 1.7, p < 0.01) and poor hygienic practices associated with manual milking (OR = 1.69, p < 0.01). The latter two factors suggest that horizontal transmission is an important route of infection. This study is the first to report the seroprevalence of and risk factors for N. caninum infection in Antioquia and allows us to conclude that N. caninum is widely distributed in this region.

Genetic characterisation of Neospora caninum strains from clinical samples of zebuine foetuses obtained in abattoirs in Goiás, Brazil.

The Neospora caninum microsatellite markers were applied to clinical samples. Genotyping technology involving fluorescently labelled DNA fragment analysis was used in combination with DNA sequencing for markers with complex repetitive sequences. Nineteen DNA samples from 15 brains and four hearts of naturally infected non-aborted zebuine foetuses from abattoirs in Goiás, Brazil. N. caninum had been detected in these foetuses by nested-PCR of the internal transcribed spacer-1 rRNA region, and the samples were analysed using these microsatellites. Seven complete or nearly complete allele profiles were obtained from six foetuses. Three distinct profiles of N. caninum were identified in a unique microregion (Meia Ponte) of Goiás. Two alleles for the same marker were detected in a unique foetus that was probably infected with two different strains. A new allele for one of the microsatellites is described. The multilocus analysis performed here revealed a preliminary means of discriminating between individual strains according to their geographical origins. These are the first results that have been obtained regarding the molecular characterisation of strains of N. caninum from infected zebuine foetuses in South America and reveal for the first time that there are genotypic differences in the strains that are responsible for foetal transmission in zebuine foetuses.

Abortions in bovines and Neospora caninum transmission in an embryo transfer center.

Neosporosis is considered to be one of the main causes of abortions in bovines. In this study we evaluated the congenital transmission and occurrence of abortions by Neospora caninum in an embryo transfer center in Neropolis, Goiás. Serological samples from 101 recipients, 61 donors, and 90 calves were analyzed. Among these animals, 32.67% of the recipients, 22.22% of the donors, and 6.66% of the calves were positive for N. caninum. The rate of vertical transmission was 24%. There was a statistically significant difference between antibody titer of the recipient cows and the serological status of the calves. There was no statistically significant relationship between N. caninum serological status and reproductive rates such as estrum repetition and embryo production. Eight abortions occurred, six (75%) in positive females and two (25%) in negative females. These results indicate that neosporosis may be an important cause of failing reproduction and that in embryo transfer centers recipients should be previously examined, and those that are seronegative for Neospora should be chosen to reduce abortion and the birth of seropositive calves.

Repellent activity of DEET against Amblyomma cajennense (Acari: Ixodidae) nymphs submitted to different laboratory bioassays.

This study was developed to evaluate the repellent activity of N,N-diethyl-3-methylbenzamide (DEET) against Amblyomma cajennense nymphs. Two repellent bioassays were compared and the effective concentration and repellent time were calculated. The fingertip test was accomplished to evaluate in vivo four concentrations of the compound (0.200; 0.100; 0.050 and 0.025 mg.cm⁻²) and the filter-paper bioassay to evaluate in vitro the two highest concentrations.The compound provided repellence higher than 90% in all concentrations and at least 95% repellency in the highest concentration over 5 hours. The effective concentration against 50% of tested nymphs (EC50) was 0.006 mg.cm⁻² and the EC99 was 0.036 mg.cm⁻². Those concentrations were lower than the ones obtained against other tick species, denoting the effectiveness of DEET against A. cajennense. The repellency time against 50% of the ticks (RT50) was 4.8 hours and the RT90 was 2.7 hours. Both bioassays were adequate to evaluate A. cajennense repellency and provided similar results; however the in vivo test is more appropriate to estimate the effective concentration and repellency time.

[Primers design and optimization of PCR and nested-PCR assays for the specific detection of Tritrichomonas foetus]. / Construção de iniciadores e otimização de ensaios de PCR e de nested-PCR para a detecção específica de Tritrichomonas foetus.

Tritrichomonas foetus is a pathogenic protozoan that causes a venereal disease in cattle known as bovine genital tricomonosis. In spite of the efficacy to recognize the target genomic DNA, the protocols so far developed for the diagnosis of this organism by PCR promote some inespecific amplifications or they are unable to discriminate T. foetus against other species within the genus. The objective of this study was to assess and optimize PCR and nested-PCR assays for the specific diagnosis of T. foetus, using novel primers selected from the alignment of sequences of the genes 18S rRNA, 5.8S rRNA, 28S rRNA and of the internal transcribed spacers of the rDNA (ITS1 and ITS2). A pair of primers was constructed for the genus-specific amplification of a 648 bp fragment and two others to amplify T. foetus species-specific fragments of 343 and 429 bp. No cross amplification was observed against Bos taurus genomic DNA neither against the DNA of usual bovine genital pathogens. Both, single and nested-PCR assays, presented analytical sensitivity to detect at least two T. foetus organisms.