Antonio Ortega-Pacheco

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.

Factors affecting the prevalence of mange-mite infestations in stray dogs of Yucatán, Mexico.

The aim of the present study was to determine the factors affecting the prevalence of mange-mite infestations in stray dogs of Yucatán, Mexico. The study was carried out in 200 stray dogs of Mérida capital city of Yucatán, Mexico. Four samples (head, thoracic-abdominal area, extremities and ear) were taken from each animal by skin scraping and examined microscopically in 10% KOH solution to detect the presence of mites. Mites were also collected from the external ear canal of dogs using cotton-tipped swabs. The prevalence of different mite species was calculated. A primary screening was performed using 2xK contingency tables of exposure variables. All variables with P< or =0.20 were analyzed by a logistic-binomial regression. The overall prevalence was 34%. Demodex canis (23.0%) was the most frequent mite, followed by Sarcoptes scabei var. canis (7.0%) and Otodectes cynotis (3.5%). The following factors were found: body condition (bad, OR: 5.35, CI 95%: 1.66-17.3; regular, OR: 3.72, CI 95%: 1.39-9.99) and the presence of macroscopic lesions of dermatosis (OR: 42.80, CI 95%: 13.65-134.24).

American Trypanosomiasis in Dogs from an Urban and Rural Area of Yucatan, Mexico

American trypanosomiasis in dogs is reported from South of the United States to Argentina and Chile. It is transmitted through the contact of dogs with reduviid insects when they feed; reduviid insects are well established in the southern state of Yucatan, Mexico. However, there are no reports available about trypanosomiasis prevalence in dogs of urban and rural areas. A cross-sectional study was performed in 345 stray dogs, 102 from a rural community of Yucatan (Tunkas) and 243 from Merida, capital city of the Yucatan state. Serum samples were obtained for detection of immunoglobulin G antibodies against Trypanosoma cruzi by indirect immunofluorescence assay and Western blot. DNA was extracted from whole blood of urban dogs for polymerase chain reaction (PCR) assay. Prevalence was determined and the risk to become infected in both urban and rural dogs was evaluated using a 2 x 2 contingency table. In addition to the effect of body condition score (BCS), the age and sex of dogs were also evaluated to determine the risk of infection. Antibody prevalence against T. cruzi in rural areas was 9.8%, whereas in urban dogs was 14.4%. When PCR results were included, prevalence in dogs from the urban area increased to 17.3%. PCR allowed the detection of active asymptomatic acute-phase disease. The risk to become infected was not different between urban and rural areas, suggesting that the vector is well adapted both to rural areas and urban sprawling. Dogs with poor BCS tended to have a higher probability of seroreactivity to T. cruzi proteins than dogs with regular or good BCS (p = 0.05).

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.

Stray dogs as reservoirs of the zoonotic agents Leptospira interrogans, Trypanosoma cruzi, and Aspergillus spp. in an urban area of Chiapas in southern Mexico.

This investigation determined the presence and prevalence of the zoonotic agents Leptospira interrogans, Trypanosoma cruzi, and Aspergillus spp. in the stray dog population (a total of 224 stray dogs) in an urban area of Southern Mexico. Blood serum samples were taken from all dogs, and root hair samples were taken from dogs with skin lesions and partial alopecia. IgG antibodies for L. interrogans from 10 serovars were detected using the microscopic agglutination test. Immunofluorescence antibody test and Western blot assay were used for serologic diagnosis of T. cruzi. The Sabouraud medium was used to isolate Aspergillus spp. Prevalence of L. interrogans was 4.9%, which was determined by identifying only serovars Pyrogenes, which accounted for 3.6%, and Tarassovi, which constituted 1.3%, with titers from 1:100 to 1:800. Additionally, T. cruzi antibodies were detected in 4.5% of the dogs. Skin lesions were found in 43% of the dogs (98/224), and 35 cultures were positive for Aspergillus spp. (35.7%, p < 0.05, 95% confidence interval 2.45-3.67), identified as A. niger (82.8%), A. flavus (14.3%), and A. terreus (2.9%). This study demonstrates the presence of certain zoonotic agents (bacteria, protozoa, and fungi) in stray dogs living within the studied area. Dogs play an important role in the transmission of diseases that are potentially harmful to humans. Although the prevalence of canine leptospirosis and trypanosomiasis is not high in Southern Mexico compared with other tropical regions of Mexico, the presence of these zoonotic agents in the stray dog population demonstrates that the stray dog population in this region is a significant reservoir and potential source of infection in humans. Special care should be taken when handling stray dogs that exhibit skin lesions with partial alopecia, since a pathological Aspergillus sp. fungus may be present.

Infection dynamic of Toxoplasma gondii in two fattening pig farms exposed to high and low cat density in an endemic region

The presence of cats in the farms is considered a risk factor for the infection of pigs with Toxoplasma gondii (T. gondii). Cats eliminate oocysts that contaminate food, water and promote the infection of host reservoir such as rodents and birds among others that are also involved in the infection of pigs. The objective of this study was to assess the dynamic of infection of T. gondii in seronegative weaned pigs from weaning to 20 weeks of age from two farms from an endemic region, one with high and low density of cats. A cohort study was performed in 64 pigs, 31 newly weaned pigs on a farm with a high density of cats (FA) and 33 newly-weaned pigs on a farm with a low density of cats (FB). Blood samples were collected every 14 days to determine the presence of IgG antibodies against T. gondii in the serum using an indirect ELISA test. True incidence rate (TIV), cumulative incidence (AI) and relative risk (RR) was calculated. The age of seroconversion was determined by using survival tables; both farms were compared with Long-Rank test. In FA 97.5% of the pigs seroconverted at the second sampling and 100% at the third sampling, while in the FB all pigs seroconverted to the fourth sampling. The TIV was 0.67 and 0.43 for FA and FB respectively, during the first four weeks at risk. A RR of 1.5 (1.04-2.39) was obtained (p<0.05). Animals of the FA had a higher risk of infection compared with the FB, however, all animals included in the study had contact with the agent. Infection with T. gondii was rapidly distributed in both farms, regardless of the relative density of cats observed during the study. These results suggest a high environmental contamination with oocysts in the facilities of both farms probably due to the fact that T. gondii infection is endemic in the area where the farms are located, allow proper establishment of the etiological agent. The points of prevention and control strategies to avoid exposure of pigs to T. gondii in an endemic area should focus on the control of cats and rodents.

Prevalence and Risk Factors of Toxoplasma gondii in Fattening Pigs Farm from Yucatan, Mexico

The objective of this study was to estimate the prevalence and identify risk factors associated with the presence of Toxoplasma gondii in pig-fattening farms from Yucatan, Mexico. A cross-sectional study was conducted with a two-stage sampling. There were 429 pigs sampled from 39 farms randomly selected. Blood samples were collected to obtain DNA and serum. The presence of IgM and IgG antibodies was determined by indirect ELISA. Prevalence was estimated by diagnostic test. Potential risk factors to be included in a marginal logistic regression were tested by chi-square or Fisher. The prevalence of IgM and IgG was 92.5% (397/429) (CI 89.9–95.1%) and 95.8% (411/429) (CI 93.7–97.8%), respectively. Regarding PCR, a prevalence of 50.8% (218/429) (CI 45.9–55.6%) was found. The logistic regression showed an association with herd size and type of feeder (P < 0.05). The risk of a case in farms with ≤400 pigs was 27.9 times higher than in farms with >400 pigs. The manual feeder was a significant protective factor associated with the seropositive against T. gondii. Results indicate a high circulation of T. gondii in pig-fattening farms from Yucatan, finding an increased risk of infection for those farms with less than 400 animals and automatic feeders.

An Epidemiological Study of Intestinal Parasites of Dogs from Yucatan, Mexico, and Their Risk to Public Health

The prevalence of intestinal parasites in dogs and factors associated were studied in a rural community of Yucatan (southern Mexico), with special attention to those gastrointestinal parasites potentially transmitted to man. One hundred thirty dogs from 91 households were studied. Fecal samples were processed by the centrifugation-flotation and the McMaster techniques. To determine factors associated with zoonotic parasites in dogs, univariate analysis was performed, using sex, age, and body condition as independent variables. Variables with p < 0.2 were analyzed by a logistic regression. Of 130 dogs, 104 were positive for the presence of intestinal parasites, representing a prevalence of 80%. Eggs of four species of helminths (Ancylostoma caninum, Thichuris vulpis, Toxocara canis, and Dipylidium caninum) and coccidian oocysts were detected. A. caninum was the most prevalent parasite (73.8%), followed by T. vulpis (25.4%), T. canis (6.2%), D. caninum (2.3%), and coccidian oocysts (2.3%). The majority of dogs were infected by only one species of parasite (70/130, 53.8%). Mixed infection caused by two or three zoonotic parasites were discovered in 21.3% (30/130) and 3.1% (4/130), respectively. A. caninum showed the highest egg output (42.3% of dogs had ≥ 500 eggs per gram). Factors associated with zoonotic parasites were age (<2 years old; odds ratio = 5.30, p = 0.029) and body condition (poor body condition; odds ratio = 6.69, p = 0.026). In conclusion, young dogs from rural Yucatan, Mexico, with poor body condition had a higher prevalence of intestinal zoonotic parasites as these factors were associated with a higher risk of becoming infected.

Frequency and Type of Renal Lesions in Dogs Naturally Infected with Leptospira Species

The aim of this study was to determine the frequency and type of renal lesions associated with positive titers against Leptospira sp. in a stray dog population. Three hundred fifty pairs of kidneys and an equal number of serum samples were collected from dogs captured by the dog pound of Merida, Yucatan, Mexico. Euthanasia of dogs was performed following the regulations of the Official Mexican Health Ministry (NOM‐033‐ZOO‐1995). Serum samples were evaluated with the microscopic agglutination test, and tissue samples were processed and fixed in paraffin. After staining with hematoxylin and eosin, the frequency of renal lesions was determined and classified. As an additional evaluation, samples with interstitial nephritis were stained by the Warthin–Starry method in order to observe the presence of spirochete forms that could be morphologically compatible with Leptospira spp. We found that 98% of cases presented at least one type of lesion. The main histological lesions found were mesangial proliferative glomerulonephritis (MPGN) in 63.7% (n= 223), mesangial proliferative glomerulonephritis and interstitial nephritis (MPGN+IN) in 34% (n= 119), nephrosclerosis in 0.57% (n= 2), mesangial glomerulonephritis in 0.28% (n= 1), and interstitial nephritis (IN) in 0.28% (n= 1). Thirty‐four percent (n= 122) of the dogs were seropositive to Leptospira sp., mainly against serovar canicola. Among dogs with IN (alone or associated with MPGN) (n= 120), 49.1% were seropositive to Leptospira sp., but only 17% of them showed spirochete forms compatible with the bacteria. A statistical association between seropositive dogs and the presence of MPGN+IN was determined (P < 0.0001; odds ratio 2.7, confidence interval 1.7–4.5). We concluded that the frequency of renal lesions found in this study is high and L. canicola is probably the most common circulating serovar in dogs from this area. Dogs that have been in contact with Leptospira spp. have a higher risk of developing renal lesions of the type MPGN+IN.

Prevalence and Risk Factors of Toxoplasma gondii Infection in Domestic Cats from the Tropics of Mexico Using Serological and Molecular Tests

The aim of this study was to determine the prevalence and risk factors associated with Toxoplasma gondii infection in domestic cats using an indirect-ELISA (IgM and IgG) and PCR. Samples collected from 220 cats from Merida, Yucatan, Mexico, were analyzed. Cases were reported as acute or chronic. Cases when positive to IgM and IgG and PCR were considered as reactivated chronic infection. Risk factors (sex, age, body condition, diet access to hunting, and number of cats in home) were assessed with a multivariate analysis, 75.5% (166/220) of the cats were IgM and 91.8% (202/220) IgG-seropositive and 79% were PCR-positive (173/220). Number of cats per household and low body condition score were associated with reactivated chronic infection (P < 0.05). It is concluded that T. gondii is scattered in the studied population with several periods of reinfection, and therefore an environmental contamination with infecting oocysts exists and there are intrinsic associated factors in cats that increase the risk of becoming infected.