RESUMEN
The study was conducted in two major dairy areas of Carlsen field and Waller field to assess the prevalence of risk factors for infection with verocytotoxigenic Escherichia coli (VTEC) by determination of selected management practices and the distribution of animal and human populations in two areas in Trinidad. Most farms in both farming areas were in the range of 11 to 25 acres in size and there was no statistically significant difference (p = 0.8) between areas. Most dairy farms, 62.1 and 48.3 per cent in Waller field and Carlsen field respectively, fell within the range of 1 to 20 cows per farm with the differences not being statistically significant (p = 0.1). In Waller field, 58 (87.9 per cent) farmers stated that they had very close contact with their pets compared with 40 (69.0 per cent) in Carlsen field. The difference was statistically significant (p = 0.01). There was a statistically significant difference (P<0.05; x2) in the distribution of persons in households between Waller field and Carlsen field. Most farms in both areas claimed to practise hand washing before and after milking, 98.5 per cent in Waller field and 100 per cent in Carlsen field. The Water and Sewerage Authority (WASA) accounted for 63.6 and 48.3 per cent of the water supply in Waller field and Carlsen field respectively, but the difference was not statistically significant (p = 0.08). Most farms in Waller field (83.3 per cent) and Carlsen field (94.8 per cent) indicated that they used the state veterinary services. It was concluded that variation in management practices on farms would affect the prevalence of VTEC across sources and species.
Asunto(s)
Animales , Industria Agropecuaria , Abastecimiento de Agua , Trinidad y TobagoRESUMEN
A cross-sectional study was conducted to determine the prevalence and characteristics of verocytotoxigenic Escherichia coli (VTEC) on 25 dairy farms each located in Waller field and Carlsen field farming areas in Trinidad. On each selected farm, faecal samples were collected from milking cows, calves and humans; rectal swabs were obtained from pet farm dogs; bulk milk was sampled as well as effluent from the milking parlour. Escherichia coli was isolated from all sources on selective media using standard methods. Isolates of E. coli were subjected to slide agglutination test using E. coli O157 antiserum, vero cell cytotoxicity assay to detect verocytotoxin (VT) and heat labile toxin (LT) production, the polymerase chain reaction (PCR) to detect VT genes, and the dry spot test to screen for E. coli O157 and non-O157 strains. In addition, faecal samples from animal and human sources were tested for VT genes using PCR. Of a total of 933 E. coli isolates tested by the slide test, eight (0.9%) were positive for the O157 strain. The vero cell cytotoxicity assay detected VT-producing strains of E. coli in 16.6%, 14.6%, 3.2% and 7.1% of isolates from cows, calves, farm dogs and humans respectively (P < 0.05; chi(2)). For LT production, the highest frequency was detected amongst isolates of E. coli from calves (10.8%) and the lowest (0.0%) amongst isolates from humans and bulk milk (P < 0.05; chi(2)). Of the 61 VT-producing isolates by vero cell cytotoxicity assay tested by PCR, the VT, LT and eae genes were detected in 62.3%, 4.9% and 1.6% respectively (P < 0.05; chi(2)). Amongst the 45 E. coli isolates that were VT positive (vero cell) or VT-gene positive by PCR, 2.2%, 2.2%, 4.4% and 6.7% belonged to non-O157 strains O91, O111, O103 and O157, respectively, as determined by the Dry spot test. Detection of VTEC strains in milk and dairy animals poses a health risk to consumers of milk originating from these farms. In addition, the demonstration of VTEC strains in humans, VT gene in faecal samples and E. coli isolates as well as non-O157 VTEC strains of E. coli are being documented for the first time in the country.
Asunto(s)
Enfermedades de los Bovinos/epidemiología , Infecciones por Escherichia coli/veterinaria , Escherichia coli , Filogenia , Toxinas Shiga/biosíntesis , Pruebas de Aglutinación , Animales , Bovinos , Enfermedades de los Bovinos/microbiología , Enfermedades de los Bovinos/transmisión , Chlorocebus aethiops , Estudios Transversales , Industria Lechera/estadística & datos numéricos , Perros , Escherichia coli/clasificación , Escherichia coli/aislamiento & purificación , Escherichia coli/metabolismo , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/microbiología , Infecciones por Escherichia coli/transmisión , Heces/microbiología , Femenino , Humanos , Leche/microbiología , Reacción en Cadena de la Polimerasa , Prevalencia , Trinidad y Tobago/epidemiología , Células Vero , ZoonosisRESUMEN
A cross-sectional study was conducted to determine the prevalence and characteristics of verocytotoxigenic Escherichia coli (VTEC) on 25 dairy farms each located in Waller field and Carlsen field farming areas in Trinidad. On each selected farm, faecal samples were collected from milking cows, calves and humans; rectal swabs were obtained from pet farm dogs; bulk milk was sampled as well as effluent from the milking parlour. Escherichia coli was isolated from all sources on selective media using standard methods. Isolates of E. coli were subjected to slide agglutination test using E. coli O157 antiserum, vero cell cytotoxicity assay to detect verocytotoxin (VT) and heat labile toxin (LT) production, the polymerase chain reaction (PCR) to detect VT genes, and the dry spot test to screen for E. coli O157 and non-O157 strains. In addition, faecal samples from animal and human sources were tested for VT genes using PCR. Of a total of 933 E. coli isolates tested by the slide test, eight (0.9 per cent) were positive for the O157 strain. The vero cell cytotoxicity assay detected VT-producing strains of E. coli in 16.6 per cent, 14.6 per cent, 3.2 per cent and 7.1 per cent of isolates from cows, calves, farm dogs and humans respectively (P < 0.05; chi(2)). For LT production, the highest frequency was detected amongst isolates of E. coli from calves (10.8 per cent) and the lowest (0.0 per cent) amongst isolates from humans and bulk milk (P < 0.05; chi(2)). Of the 61 VT-producing isolates by vero cell cytotoxicity assay tested by PCR, the VT, LT and eae genes were detected in 62.3 per cent, 4.9 per cent and 1.6 per cent respectively (P < 0.05; chi(2)). Amongst the 45 E. coli isolates that were VT positive (vero cell) or VT-gene positive by PCR, 2.2 per cent, 2.2 per cent, 4.4 per cent and 6.7 per cent belonged to non-O157 strains O91, O111, O103 and O157, respectively, as determined by the Dry spot test...