Anaplasma marginale es la protobacteria de mayor prevalencia en el ganado bovino a nivel mundial. Este patógeno se multiplica en los eritrocitos y endotelio causando la enfermedad hemolítica denominada anaplasmosis, que en su fase aguda se acompaña de anemia, pérdida de peso e incluso la muerte. Se asume que el microorganismo es transmitido biológicamente por ixódidos, mecánicamente por dípteros hematófagos, iatrogénicamente o por vía transplacentaria. Con el fin de detectar la presencia de A. marginale en becerros neonatos de un rebaño Brahman del estado Yaracuy, Venezuela, se colectaron muestras de sangre de 29 crías con menos de 24 horas de nacidas y sus correspondientes madres recién paridas. El ADN obtenido de las 58 muestras fue sometido a una PCR anidada (PCRa) específica para el diagnóstico de Anaplasma spp. Adicionalmente a los sueros de las 29 madres se les realizó un ELISA competitivo (ELISAc) para el diagnóstico de anaplasmosis utilizando el protocolo señalado por la casa comercial VMRD. Los resultados mostraron que en el 20,69% de las crías (6 neonatos) se obtuvo amplificación del gen msp5 de Anaplasma spp, mientras que todas las muestras de las madres eran positivas a la PCRa y al ELISAc. La evidencia experimental obtenida indica que la presencia de la protobacteria en animales con menos de 24 horas de nacidos es producto de la transmisión transplacentaria de la madre infectada al feto durante la gestación y pone de manifiesto que bajo las condiciones estudiadas esta vía de transmisión es importante en la diseminación del patógeno.

Anaplasma marginale is the most prevalent protobacteria in cattle worldwide. This pathogen multiplies in the erythrocytes and endothelium causing a hemolytic disease called anaplasmosis, which in its acute phase is accompanied by anemia, weight loss and even death. It is assumed that the organism is transmitted biologically by ixodides, mechanically by haematophagous dipterans, iatrogenically or by transplacental transmission. In order to detect neonatal anaplasmosis in a Brahman herd of the Yaracuy State, Venezuela, blood samples were collected from 29 calves less than 24 hours old and their postpartum mothers. The DNA obtained from 58 samples was subjected to a nested PCR (nPCR) specific for the diagnosis of Anaplasma spp. In addition the serum of the 29 mothers was evaluated by a competitive ELISA (ELISAc) for diagnosis of anaplasmosis using the protocol indicated by the commercial house VMRD. The results showed that in 20.69% of the offspring (6 calves) gene amplification was obtained from msp5 of Anaplasma spp, while all the samples from the mothers were positive for nPCR and ELISAc. The experimental evidence obtained indicates that the presence of protobacteria in animals less than 24 hours of birth is the result of transplacental transmission from the infected mother to the fetus during pregnancy and shows that under the studied conditions this route of transmission is important in the spread of the pathogen.

From September 2001 through September 2002, house fly and stable fly pupae were collected weekly from three fly habitats at the University of Florida Research dairy in northcentral Florida and evaluated for parasitism. Varying parasitism percentages were observed throughout the study but they were not affected by temperature, precipitation or fly abundance. Of the 6,222 house fly pupae and 1,660 stable fly pupae that produced either a host fly or a parasitoid, 26.9% and 26.7% were parasitized, respectively. Ten parasitoid species were recovered, with the genus Spalangia accounting for 85.7% of the total; the most common parasitoids attacking house fly and stable fly pupae were Spalangia endius Walker (33.9% and 27.3%), S. cameroni Perkins (27.9% and 40.6%), and S. nigroaenea Curtis (21.0% and 24.8%), respectively. Other parasitoids included one specimen of S. erythromera Förster and four specimens of Phygadeuon fumator Gravenhörst (Ichneumonidae). The percentage parasitism of pupae collected from bunker silos was higher than that of pupae from calf pens and open pastures. Spalangia cameroni was consistently recovered through the entire year. Spalangia nigroaenea was predominant in July, August, and September. Spalangia endius was most active from October to May with a peak of relative abundance in January.

El objetivo de esta investigación fue identificar los factores de riesgo asociados a la tripanosomosis bovina en explotaciones ganaderas de Venezuela. Se procesaron 1.675 muestras para el estudio de la infección activa (IA) y 1.572 para serología, procedentes de 49 explotaciones ganaderas distribuidas en 4 regiones geográficas: llanos (orientales y occidentales), sur del lago, centro-occidental y andina. La IA se determinó por la técnica de microcentrifugación y la seropositividad a Trypanosoma vivax fue detectada mediante las técnicas de inmunofluorescencia indirecta y el ensayo inmunoenzimático ELISA. A través de una encuesta epidemiológica se recabó información sobre tipo racial, edad, sexo, propósito, manejo y tratamiento tripanocida (principio activo y frecuencia de aplicación). Se obtuvo una tasa de infección activa general de 5,9% y una seropositividad general de 33,1%. Los siguientes parámetros (factores de riesgo) tuvieron asociación positiva con la seropositividad: ausencia de aplicación de drogas tripanocidas (OR=2,62), uso de diminaceno (OR=1,87), grupo etario mautes(as) (OR=1,48) y adultos (OR=1,41), tipo racial Bos indicus (OR=1,80), propósito carne (OR=1,29) y manejo semiintensivo (OR=1,40). Los factores asociados negativamente (efecto protector) fueron: aplicación de drogas tripanocidas (independientemente del principio activo; OR=0,38), aplicación de isometamidio (OR=0,35), frecuencia de uso de drogas tripanocidas de forma regular con intervalo de 4 a 6 meses (OR=0,62) y mayor a 6 meses (OR=0,33), grupo etario becerros (as) (OR=0,39), tipo racial mestizos de Bos taurus por B. indicus (OR=0,63) y manejo extensivo (OR=0,71). Estos factores deben ser considerados en la implementación de planes estratégicos de control en áreas endémicas de esta enfermedad

The aim of this study was to identify the risk factors associated with bovine tripanosomosis in cattle ranches in Venezuela. There were processed a total of 1.675 blood samples for active infection study and 1.572 for serology, collected in 49 cattle herds from livestock farms scattered in nine states of the country and 4 different geographical regions: east and west plains, south lake, central-west, and andean. Microcentrifugation technique was used to detect active infection by Trypanosoma vivax, while seropositivity to this hemoprotozoan was detected by both the indirect immunofluorescence technique and the ELISA immunosorbent assay. Through an epidemiological survey, information on the racial, age, gender, purpose, management, and tripanocidal treatment (active ingredient and frequency of application) was gathered. There was a general active infection rate of 5,9% and an overall 33,1% seropositivity. The following parameters (risk factors) were positive associated to seropositivity: lack of implementation of trypanocidal drugs (OR=2,62), use of diminazeno (OR=1,87), age group heifers(OR=1,48) and adults (OR=1,41), racial Bos indicus (OR=1,80), purpose meat (OR=1,29), and semi intensive handling (OR = 1,40). Factors associated negative (protective effect) were trypanocidal drug application (irrespective of the active ingredient) (OR=0,38), implementing isometamidium (OR=0,35), frequency of use of drugs on a regular basis with trypanocidal drugs at interval of 4 to 6 months (OR=0,62) and longer than 6 months (OR=0,33), age group calves (OR=0,39), racial mixed breed B. taurus x B. indicus (OR=0,63), and extensive management (OR=0,71). These factors should be considered in the implementation of strategic plans to control this disease in endemic areas

Un total de 50 caninos de áreas rurales de los estados Lara, Yaracuy, Carabobo y Falcón, Venezuela, fueron examinados visualmente y mediante palpación cutánea con el fin de detectar la presencia de garrapatas. Ninguno de los animales se encontró parasitado por Rhipicephalus sanguineus, la garrapata común del perro. Se colectaron 139 especimenes adultos del género Amblyomma Koch, 1844: 72 hembras y 65 machos de la especie Amblyomma ovale Koch, 1844, y dos hembras de la especie Amblyomma triste Koch, 1844. La identificación de los especimenes se realizó mediante observación en lupa estereoscópica y con la ayuda de claves taxonómicas. Los Estados donde se colectó el mayor número de ixódidos fueron Falcón con 52 especimenes y Lara con 49, representando 38 y 36%, respectivamente. A. ovale ha sido reportada como vector natural de Hepatozoon canis en áreas rurales. La especie A. triste fue colectada sólo en un canino del estado Yaracuy. Esta especie ha sido incriminada como el vector biológico de varios agentes rickettsiales patógenos, tanto para humanos como para animales domésticos y salvajes, por lo que se resalta la importancia del género Amblyomma en la transmisión de enfermedades zoonóticas.

Fifty dogs from the rural areas of Lara, Yaracuy, Carabobo and Falcón States of Venezuela were sampled through the visual and touch techniques in search of the presence of ticks. All the dogs were free of the brown dog tick Rhipicephalus sanguineus. A total of 139 adult ticks of the genus Amblyomma Koch, 1844 were collected: of them, 65 males and 72 females were identified as Amblyomma ovale Koch, 1844, whereas two females belonged to the species Amblyomma triste Koch, 1844. The observation through stereomicroscope, as well as the use of taxonomic keys, were employed in the identification of the collected specimens. Most of the ticks were collected in Falcón and Lara States, totalling 52 (38%) and 49 (36%), respectively. The species A. ovale has been reported as a natural vector of the protozoan Hepatozoon canis in rural areas. A. triste was collected only in one dog in Yaracuy State. This species has been incriminated as a biological vector of several rickettsial agents to the men and animals. The actual role of the genus Amblyomma as vector of zoonotic disease agents is highlighted.

El amitraz es un principio activo ampliamente utilizado en Venezuela para el control de garrapatas en bovinos, habiéndose detectado fallas en el control de la especie Boophilus microplus. El objetivo de este trabajo fue determinar la eficacia in vitro del amitraz en B. microplus utilizando cinco concentraciones distintas, incluyendo la terapéutica (208 ppm). Se utilizaron 240 teleoginas colectadas de cuatro explotaciones lecheras del estado Lara, en número de 60 por finca y divididas en grupos de 10 cada uno, con un peso promedio de 220 mg/garrapata. Se realizó el test de inmersión de adultos a cinco grupos con una preparación comercial de amitraz (12,5%) a las concentraciones de 52, 104, 208, 416 y 832 ppm, sumergiéndolas por tres minutos en cada preparación. El grupo control fue sumergido en agua. Durante 18 días se incubaron a una temperatura promedio de 27°C y humedad relativa de 85%. Posteriormente se pesó la masa total de huevos producidos por cada grupo y se incubaron por 21 días. Se realizó el contaje de larvas emergidas y huevos que no eclosionaron en cada tubo y se estimó el porcentaje de eclosión para luego calcular la eficiencia reproductiva, eficacia y factor de resistencia. Las cuatro poblaciones de B. microplus estudiadas resultaron resistentes a amitraz, no encontrándose diferencias significativas entre la eficacia de la concentración recomendada por los fabricantes y la de concentraciones superiores de amitraz.

In Venezuela, the acaricide amitraz is widely used to control tick infestations in cattle, and therapeutic failures in the control of the Boophilus microplus species have been detected. The aim of this work was to determine the in vitro efficacy of amitraz on B. microplus using five different concentrations, including the manufacturer’s recommended dosage (208 ppm), through the adult immersion test (Drummond test). A sample of 240 engorged females was collected from dairy farms in Lara state, (60 ticks/farm), divided in groups of 10 ticks averaging 220 mg/tick. Commercial amitraz formulation (12.5%) was used to prepare the working concentrations of 52, 104, 208, 416 and 832 ppm. The control group was submerged in water. Ticks were placed in glass lamina and incubated at 27ºC and 85% R.H for 18 days. The eggs masses were collected, weighted, separated in vials and allowed to hatch at 85% R.H. and 27º C for 21 days. Both the emerged larvae and eggs were quantified in each tube in order to determine the reproductive efficiency, efficacy percentage and the resistance factor. The four populations of B. microplus studied were resistant to amitraz. Statistical significant differences between the effectiveness of highest concentration of amitraz and that recommended by the manufacturer were not observed.

La garrapata Boophilus microplus está distribuida por todo el mundo y es de gran importancia económica por las pérdidas que ocasiona en rebaños bovinos. El objetivo de este trabajo fue determinar la susceptibilidad in vitro al coumafos en cuatro poblaciones de garrapatas adultas, utilizando cinco concentraciones distintas de este principio activo, incluyendo la recomendada por el fabricante (terapéutica), y el porcentaje de mortalidad en larvas utilizando dosis terapéutica. Se utilizaron 240 teleoginas (garrapatas hembras adultas ingurgitadas) de cuatro fincas lecheras del estado Lara, un total de 60 garrapatas/finca divididas en grupos de 10 c/u, conformando 6 grupos/finca; fueron tratados individualmente cinco grupos con coumafos a las concentraciones de 125, 250, 500, 1.000 y 2.000 ppm y un grupo control con agua solamente, utilizando la técnica de inmersión de adultos. Larvas obtenidas de esta misma población fueron sometidas a la técnica de inmersión de larvas de Shaw. La media del peso de la masa total de huevos fue menor en forma significativa en los grupos tratados con concentraciones de 1000 y 2000 ppm de coumafos con respecto al grupo control en la finca 1. No se observaron diferencias entre los grupos tratados a las concentraciones de 125, 250, 500, 1.000 y 2.000 ppm en las cuatro poblaciones de garrapatas estudiadas por separado. La eficacia no presentó diferencias significativas entre los grupos tratados con las cinco concentraciones evaluadas en cada finca; el incremento de la concentración de coumafos no fue directamente proporcional a la eficacia. Los adultos de B. microplus resultaron resistentes al coumafos; sin embargo, se observó un 100% de mortalidad en larvas, lo que indica alta susceptibilidad de las larvas a este organofosforado

The cattle tick Boophilus microplus is widely distributed in the world and causes significant economic losses. The aim of this work was to determine in vitro susceptibility of coumaphos ixodicide in adult ticks using five different concentrations including the manufacturer’s recommended dosage, and the larvae mortality using therapeutic dose. A sample of 240 engorged females was collected from four dairy farms in Lara state, (60 ticks/farm), divided in groups of 10 ticks averaging 220 mg/tick. Commercial coumaphos formulation (20%) was used to prepare the working concentrations of 125, 250, 500, 1000 and 2000 ppm for the adults immersion test (AIT), and the control group was submerged in water. The Shaw larvae immersion test was applied in larvae obtained of this ticks population. In farm 1, weight average of the total egg masses was significantly smaller in the groups treated with coumaphos at concentrations of 1000 and 2000 ppm with respect to control group. Differences were not observed between the groups treated at the concentrations of 125, 250, 500, 1000 and 2000 ppm in each of the four farms. Statistical differences not were observed in the efficacy among groups. Higher concentrations of coumaphos did not increase the efficacy of the product. The adult ticks of B. microplus were resistant to coumaphos. Mortality in larvae reached 100%.

Boophilus microplus infestation is one of the most serious limitations to cattle industry in tropical regions, even though bovines show natural resistance to ticks. This resistance was evaluated in Cross-bred Carora Bulls (CCB) a tropicalized dairy breed from Venezuela. Seven CCB were experimentally infested with B. microplus larvae, "Mozo" strain, they were considered tick-naive because they had never been infested with ticks. The mean inoculum size applied on each bull was 6 477 larvae. After life cycle was completed adult female body weight (BW), egg mass weight (EW), egg hatching rate (%EH), and reproductive index (RI) were recorded. Results revealed a high variability in the levels of resistance to B. microplus. Thus, one animal showed greater resistance (Dunnett, p< 0.05) for the analyzed parameters in contrast with three non-resistant bulls. The others had moderate resistance. The trait "resistance" should be included togheter with other traits often used in genetic selection of cattle.