Jorge C. Rodríguez-Buenfil

A survey of dog populations in urban and rural areas of Yucatan, Mexico

ABSTRACT A survey in a major Mexican city (Merida) and three rural communities was conducted to generate information regarding the size and structure of the owned-dog populations and peoples opinions about the dogs and how they took care of them. Household characteristics and dog population size, health and reproductive issues were compared between the two kinds of communities: urban and rural. A telephone survey was conducted in Merida city whereas personal interviews were used in the rural communities. Local veterinarians were also interviewed to evaluate their influence on the dog populations in Merida city. The ratio of people to dogs was 3.4:1 in the city, and 1.7:1 to 4.6:1 in the different rural communities. In general it was more common to find a dog-owning household in the city of Merida (72.8%) than in the rural areas (63.6%, 65.5% and 71.1%), and in the city more households had adequate fences to restrain dogs. Larger families were more likely to own a dog than small families. Households of medium socio-economic status had a significantly higher probability of owning a dog than households of low or high socio-economic status. Of the dogs in the city, 90.1% were vaccinated against rabies compared with 62.3% of the dogs in the rural communities. Most animals were intact; the frequency of neutering/spaying was 3.1% in Merida and 1.8% in the rural communities. Few private veterinary practitioners were involved in the control of dog overpopulation. It is concluded that dogs are popular pets both in urban and rural Yucatan. Peoples opinions about dogs and the level of supervision varied with socio-economic status, and people in the city provided better food, shelter and preventive medicine. The veterinary practitioners did little to promote the control of dog breeding or to reduce the relinquishing of unwanted dogs in the city. Better client education and the promotion of sterilization of pets at low cost would improve the situation.

Serological survey of canine leptospirosis in the tropics of Yucatan Mexico using two different tests

Blood samples were taken from 400 stray dogs. The microscopic agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA) test were implemented using Leptospira interrogans serogroups canicola, hardjo, pyrogenes, panama, pomona, tarassovi, icterohaemorrhagiae, gryppotyphosa, wolffi and brastislava. For the ELISA test, sonicated antigen from above mentioned cultures was used. A conjugate AP-labeled anti-dog IgG antibody was used, the optimal cut-off point of ELISA was set at 1.34. Concordance between ELISA and MAT titers was measured by kappa (kappa). Overall prevalence was 35%. The most prevalent serogroups were canicola and icterohaemorrhagiae. Positive samples showed titers between 1:100 and 1:25,600, with higher titers found in serogroups canicola and icterohaemorrhagiae. Positive serum samples fell within a range of 1.36-1.65. A correlation index of 96% was found between MAT and ELISA. The sensitivity of ELISA was 98.6% and specificity 95.8%. Seroprevalence of canine leptospirosis and titers were high as a direct consequence of environmental conditions in the studied area. The ELISA test showed a good sensitivity, resulting in a good alternative test for the detection of leptospiral antibodies in dog serum.

Prevalence of pediculosis capitis in children from a rural school in Yucatan, Mexico

We conducted an analytical cross-sectional survey to estimate the prevalence of and factors associated with active head lice infestation. In total 140 children, aged 6 to 16-years, from a public school in rural Yucatan, Mexico, were examined by wet-combing. A structured questionnaire was used to collect information on individuals and the conditions in the surrounding environment. Head lice infestation was found in 19 out of the 140 children tested (13.6%) and this was associated with both lower income (OR 9.9, 95% CI 2.15-45.79, p = 0.003) and a higher frequency of hair washing (OR 8, 95% CI 1.58-50, p = 0.012). Intersectoral control programs that take into account the socioeconomic differences of children should be implemented.

Serological survey of Ehrlichia canis in stray dogs from Yucatan, Mexico, using two different diagnostic tests.

Canine ehrlichiosis is a disease produced by the rickettsial organism Ehrlichia canis. Reported prevalence may vary greatly depending on the test and sampling method used. For the serological detection of antibodies against E. canis, the indirect immunofluorescence antibody test (IFA) is considered the gold standard. However, other available serological techniques such as the indirect immunoperoxidase technique (IPT) have not yet been tested and may be efficient in detecting specific antibodies. Prevalence found (8.7% and 8.1% for IFA and IPT, respectively) was lower than previously reported in the studied area despite the well-established technique used for the determination of antigens. A kappa value of 0.958 (95% CI 0.9-1.0) was found with a sensitivity and specificity for IPT of 92.59% (95% CI 80.8-99.9) and 99.9% (95% CI 99.8 -100), respectively. The positive predictive value was 99.9% and the negative predictive value was 99.29%. The IPT technique can be used safely for serological determination of E. canis antibodies.

Risk factors for Aujeszky’s disease in pig herds and detection of field virus antibodies in fattening pigs in the state of Yucatan, Mexico

Two epidemiological studies were conducted from August 1997 to May 1998: a case-control study to identify herd level risk factors for antibodies to Aujeszkys disease virus (ADV) in sows in the state of Yucatan, Mexico and a cross-sectional study to determine the prevalence of antibodies against ADV in fattening pigs. In the case-control study, data on herd management and biosecurity were obtained from all the 27 ADV known field-virus-seropositive farms (cases) and 62 randomly selected seronegative farms (controls) by questionnaire. Breeding animals of these seropositive farms had received a gE-deletion vaccine. In the cross-sectional study, 26 farrow-to-finish farms of the 27 seropositive farms were used and blood samples taken from 60 fattening pigs per herd (15 pigs for each stage of production). Serum samples were analyzed by the screening-ELISA and gE-ELISA tests. In the case-control study, three of the 15 risk factors were significant. Odds ratios for distance to the nearest farm (< or = 2.5km), not sampling for the detection of ADV and herds with origin of breeding animals within the state were 9.5, 18.1 and 8.7. In the cross-sectional study, 11 (42.3%) of the 26 sampled farms were seropositive to vaccine antibodies. None of the piglets were positive to antibodies against field virus risk--suggesting that the strategy of vaccinating only the breeding animals reduced the ADV infection of the piglets.

Estudio serológico de la Tripanosomiasis Americana y factores asociados en perros de una comunidad rural de Yucatán, México

La Enfermedad de Chagas es producida por el protozoario Trypanosoma cruzi que causa una infeccion ampliamente diseminada en vertebrados, incluido el hombre. Escasas investigaciones han reportado la frecuencia serologica y los factores asociados a la exposicion de T. cruzi en las poblaciones caninas de comunidades rurales de Yucatan. El presente estudio tiene por objetivo estimar la frecuencia serologica e identificar factores asociados a anticuerpos anti- T. cruzi en perros de una comunidad rural de Yucatan, Mexico. Se realizo un estudio por conveniencia en 117 perros de la comunidad rural. Se tomaron muestras de sangre de cada perro para la obtencion del suero. Las muestras fueron analizadas mediante una prueba de inmunocromatografia para detectar anticuerpos anti- T. cruzi. A los propietarios de los perros se les aplico un cuestionario para identificar posibles factores de riesgos asociados a la seropositividad. Las variables de respuesta fueron analizadas mediante Chi cuadrado y las variables con P 1 ano de edad, OR= 3,8 P = 0,02), lugar donde habitan los perro (perros en el peridomicilio, OR= 6,4 P = 0,04) y presencia de triatominos en las casas (OR = 4,7 P = 0,006). Se concluye que los perros de la comunidad bajo estudio presentan anticuerpos anti- T. cruzi (29,9% de frecuencia) y tres factores se asocian a perros serologicamente positivos (perros adultos, perros que viven en el peridomicilio y presencia de triatominos en la casa)

Prevalence of Dirofilaria immitis Infection in Dogs from Celestun, Mexico, Using Polymerase Chain Reaction Test

The aim of this study was to determine the prevalence of Dirofilaria immitis in dogs and to analyze risk factors associated with infection at Celestun, a coastal locality in southeast Mexico. Blood samples were collected from 279 asymptomatic individuals between August 2007 and March 2008 and analyzed by polymerase chain reaction technique. The association between D. immitis infection and sex, age group, and distance of residence from a wetland of dogs was statistically analyzed. Prevalence of D. immitis infection was of 59.8%. Age of individuals (>2 years) was a risk factor for infection with D. immitis (odds ratio 2.49, confidence interval 1.47-4.23, p=0.001). In conclusion, Celestun can be considered a focus of D. immitis infection with high levels of transmission among the local dog population, as confirmed by the high prevalence reported and the association of age (dogs >2 years) as a risk associated with infection.

CHICKEN COOPS, Triatoma dimidiata INFESTATION AND ITS INFECTION WITH Trypanosoma cruzi IN A RURAL VILLAGE OF YUCATAN, MEXICO

This study longitudinally investigated the association between Triatoma dimidiata infestation, triatomine infection with Trypanosoma cruzi and household/backyard environmental characteristics in 101 homesteads in Molas and Yucatan, Mexico, between November 2009 (rainy season) and May 2010 (dry season). Logistic regression models tested the associations between insect infestation/infection and potential household-level risk factors. A total of 200 T. dimidiata were collected from 35.6% of the homesteads, mostly (73%) from the peridomicile. Of all the insects collected, 48% were infected with T. cruzi. Infected insects were collected in 31.6% of the homesteads (54.1% and 45.9% intra- and peridomiciliary, respectively). Approximately 30% of all triatomines collected were found in chicken coops. The presence of a chicken coop in the backyard of a homestead was significantly associated with both the odds of finding T. dimidiata (OR = 4.10, CI 95% = 1.61-10.43, p = 0.003) and the presence of triatomines infected with T. cruzi (OR = 3.37, CI 95% = 1.36-8.33, p = 0.006). The results of this study emphasize the relevance of chicken coops as a putative source of T. dimidiata populations and a potential risk for T. cruzi transmission.