Genetic polymorphism in Taenia solium cysticerci recovered from experimental infections in pigs.

Taenia solium cysticerci recovered from naturally infected pigs from Mexico, Honduras and Tanzania show a clonal structure and local lineages with probable events of genetic recombination without genetic flow within them, as revealed by RAPD. To evaluate genetic polymorphism from cysticerci recovered from experimental infections, 4 pigs were infected with T. solium eggs obtained from tapeworms released by 3 human carriers, a 10-year-old female, a 25-year-old female, and a 44-year-old male, the 4th pig was infected with a mixture of eggs from the 3 tapeworms. Each pig was orally inoculated with 50,000 eggs. After 16 weeks pigs were humanely euthanized and cysticerci were excised. Parasites recovered from each pig were analyzed by RAPD. The proportion of polymorphic loci and the mean heterozygosity as well as a dendogram and an analysis of principal coordinate and minimum spanning tree were obtained. All four pigs developed viable cysticerci; the percent infection was obtained from the ratio of the number of eggs used for infection and the number of cysticerci counted in each pig after necropsy. Infection varied from 0.2 to 4.2%. The values obtained for the proportion of polymorphic loci (0.14-0.55) and the average of expected heterozygosity (0.06-0.22) in the present experimental infection had a broader range than those reported in the literature from natural infections. The dendogram obtained clustered cysticerci into two main groups; the minimum spanning tree allowed to corroborate the data obtained in the dendogram and gave a better discrimination because in a three-dimensional plot it was easier to see that all cysticerci from each tapeworm were clustered amongst themselves. The results obtained could be hypothetically explained because environmental factors and genetic selection agents present in nature influence natural infections but do not participate in experimental ones.

Discrimination between six species of canine microfilariae by a single polymerase chain reaction.

Canine dirofilariasis caused by Dirofilaria immitis is usually diagnosed by specific antigen testing and/or identification of microfilariae. However, D. immitis and at least six other filariae can produce canine microfilaremias with negative heartworm antigen tests. Discriminating these can be of clinical importance. To resolve discordant diagnoses by two diagnostic laboratories in an antigen-negative, microfilaremic dog recently imported into the US from Europe we developed a simple molecular method of identifying different microfilariae, and subsequently validated our method against six different filariae known to infect dogs by amplifying ribosomal DNA spacer sequences by polymerase chain reaction using common and species-specific primers, and sequencing the products to confirm the genotype of the filariae. We identified the filaria in this dog as D. repens. This is the first case of D. repens infection in the United States. Additionally, we examined microfilariae from five additional antigen-negative, microfilaremic dogs and successfully identified the infecting parasite in each case. Our diagnoses differed from the initial morphological diagnosis in three of these cases, demonstrating the inaccuracy of morphological diagnosis. In each case, microfilariae identified morphologically as A. reconditum were identified as D. immitis by molecular methods. Finally, we demonstrated that our PCR method should amplify DNA from at least two additional filariae (Onchocerca and Mansonella), suggesting that this method may be suitable for genotyping all members of the family Onchocercidae.

Induction of protection against porcine cysticercosis by vaccination with recombinant oncosphere antigens.

Two recombinant Taenia solium oncosphere antigens, designated TSOL18 and TSOL45-1A, were investigated as vaccines to prevent transmission of the zoonotic disease cysticercosis through pigs. Both antigens were effective in inducing very high levels of protection (up to 100%) in three independent vaccine trials in pigs against experimental challenge infection with T. solium eggs, which were undertaken in Mexico and Cameroon. This is the highest level of protection that has been achieved against T. solium infection in pigs by vaccination with a defined antigen. TSOL18 and TSOL45-1A provide the basis for development of a highly effective practical vaccine that could assist in the control and, potentially, the eradication of human neurocysticercosis.

Detection of genetic variation in Taenia solium.

Genetic variability among Taenia solium isolates was studied in 160 cysticerci from 6 pigs, 4 from Mexico, 1 from Honduras, and 1 from Tanzania. Random amplified polymorphic DNA (RAPD) analysis performed with 4 commercial primers showed 88% polymorphic loci and an average heterozygosity of 0.077; however, several alleles were fixed within each isolate. Linkage disequilibrium analysis indicated that 3 of the 6 isolates had a random association of alleles, whereas the other 3 had a clonal structure. These results suggest the existence of local lineages in T. solium, with events of genetic recombination within them.

Prevalencia de Dirofilaria immitis en perros callejeros de la ciudad de Mérida, Yucatán, México / Prevalence of Dirofilaria immitis in stray dogs in the city of Merida, Yucatan, Mexico

Se estudió la dirofilariasis canina en la ciudad de Mérida Yucatán, en el sureste de México, con el objetivo de determinar su prevalencia y comparar la efectividad de la prueba de gota gruesa y Knott modificada , con la presencia de parásitos adultos en la necropsia. prevaleció Dirofilaria immitis en 6.54 por ciento y Dipetalonema reconditum en 7.47 por ciento. La prueba de Knott modificada detectó 11 casos positivos a microfiliarias circulantes y la prueba de gota gruesa solamente detectó 3 casos. Se encontraron 2 casos de filariasis mixta. Cinco animales fueron positivos a parásitos adultos en la necropsia y 7 positivos a microfiliarias circulantes; sin embargo, 2 casos con parásitos adultos en la necropsia no pudieron ser detectados por la técnica de knott modificada, y 2 casos positivos a Knott modificada no presentaron parásitos adultos a la necropsia. Se presentó un promedio de 6 parásitos adultos por cada positivos; los parásitos fueron localizados en distintas partes del corazón. Se hallaron 3 casos positivos a larvas de Dipetalonema reconditum en la orina, lo que representa 5.54 por ciento de positividad. Se concluye que para el diagnóstico de la dirofilariasis canina es necesario la detección de microfilarias en sangre y acompañarse de pruebas complementarias

Epizootiología de los parásitos gastrointestinales en bovinos del estado de Yucatán / Epidemiological study of gastrointestinal parasited in bovines in the Satate of Yucatán, Mexico

Se realizó un estudio epizootiológico durante un periodo de dos años en bovinos jóvenes (criados en el estado de Yucatán) bajo condiciones de clima tropical, para conocer los parásitos gastrointestinales, su prevalencia y variación estacional mediante exámenes coproparasitoscópicos, la recolección de larvas de pasto y necropsia de animales. Se seleccionaron tres zonas según la climatología. En cada zona se eligieron cuatro ranchos, que se dividieron en dos grupos, de acuerdo con su población animal. Cada dos meses, 20 bovinos de cada rancho fueron muestreados. El muestreo se inició con becerros de dos y medio meses de edad promedio hasta completar un año. Para confirmar los resultados se realizó una repetición en el siguiente año. Los parásitos identificados fueron: diez especies del protozoario Eimeria sp y los nematodos: Toxocara sp, Strongyloides sp, Bunostomum sp, Oesophagostomum sp, Mammomonogamus sp, Trichostrongylus sp, Ostertagia sp, Cooperia sp, Haemonchus sp, Trichuris sp y el cestodo Monieziea sp. Las especies de Eimeria más prevalentes fueron: E. auburnesis, E. bovis y E. ellipsoidalis. Dentro de los nematodos, sobresalen los del orden Strongylida, de éstos prevalecieron: Trichostrongylus sp, Cooperia sp y Haemonchus sp. El análisis estadístico reveló que sólo la variable edad es altamente significativa para los parásitos del orden Strongylida y del género Trichuris. El número de huevecillos del orden Strongylida se incrementó a los tres meses de edad de los animales y declinó paulatinamente a los 13 meses de edad, cuando finalizó la prueba. Por tanto, se considera que la etapa crítica de máxima infección se encuentra entre los seis y nueve meses de edad. El tratamiento antihelmíntico con Febantel a una dosis de 5 mg/kg por vía oral cada dos meses duarnte el primer año, no tuvo efecto significativo en la excreción de formas parasitarias