A preliminary survey of Trichinella spp. in pigs raised under controlled housing conditions in Colombia: 2014-2016.

A preliminary survey of Trichinella spp. infection was conducted in Colombian swine herds between 2014 and 2016. A total of 1,773 pigs reared on farms under controlled housing conditions and processed in 34 slaughterhouses were tested either by the artificial digestion of pooled muscle samples (n = 1,173) or by serology (n = 600). In addition, 550 rats trapped on 29 swine farm premises were also tested by artificial digestion. No positive pig samples were detected. Similarly, no Trichinella spp. muscle larvae were detected in rats. These results are in agreement with the lack of historical Trichinella infection reports in domestic and wild animals and humans in Colombia. However, a more extensive epidemiological investigation and a continuous surveillance program are needed to continue declaring swine herds in Colombia free of Trichinella infection.

Multi-drug resistant Haemonchus contortus in a sheep flock in Antioquia, Colombia.

A sheep farm experiencing high lamb mortality and poor body conditions of ewes due to haemonchosis was tested for the presence of anthelmintic-resistant nematodes in August 2014. A fecal egg count reduction test was performed in Colombia on this farm and a DrenchRite® Larval development Assay (LDA) was shipped to the University of Georgia in the United States for resistance testing. The fecal egg count reduction test (FECRT) was conducted on 70 out of 500 animals allocated into five groups of 14 animals each: untreated control, albendazole (ABZ; 3.5mg/kg sc), ivermectin (IVM; 0.2mg/kg sc), moxidectin (MOX; 0.2mg/kg sc) and levamisole (LEV; 5mg/kg sc) plus triclabendazol/ivermectin (TBZ; 10mg/kg and IVM; 0.2mg/kg po). Individual fecal egg counts (FEC) using the modified McMaster technique and pooled larval cultures were performed 10days after anthelmintic treatment. Following 10days the initial results from the ABZ and IVM groups, 24 animals were treated twice with trichlorfon (TCF; 50mg/kg po) on days 0 and 6, and then checked for FEC on day 10. Mean differences in FEC before and after treatment were negligible (3 to 8% change) for the control, ABZ, LEV-TBZ and IVM groups. The MOX treatment resulted a mean FEC reduction of 76.7%, which was not-significant by t-test (p=0.08). The TCF treatment showed a mean FEC reduction of 42.3%, which was also not-significant (p=0.1). The DrenchRite® LDA was used to evaluate the resistance status to benzimidazole, levamisole, ivermectin and moxidectin on this farm. Coprocultures indicated that the predominant worm species was Haemonchus contortus (Colombia 94-100%) (UGA 77% H. contortus and 23% Trichostrongylus colubriformis). Resistance was evaluated for both H. contortus and T. colubriformis. The LDA results indicated high resistance to all 4 anthelmintics for both parasite species. The current study, together with similar surveys in 4 other Antioquian goat and sheep farms, confirms the presence of multi-drug resistant H. contortus to all three classes of anthelmintics in this region of Colombia.

Ivermectin resistance of three Rhipicephalus microplus populations using the larval immersion test / Resistencia de tres poblaciones de Rhipicephalus microplus a la ivermectina por el ensayo de inmersión de larvas / Resistência de três populações de Rhipicephalus microplus à ivermectina pelo teste de imersão de larvas

Background: in Colombia, the control of tick infestation in cattle is almost exclusively performed with chemical acaricides. It is important to determine the degree of resistance of Riphicephalus microplus field populations to ivermectins (IVM) as the first step to design strategies to increase the useful life of acaricides and decrease the reliance on chemical controls. Objective: to test the degree of resistance to IVM. Methods: three cattle farms in Antioquia (Colombia) where IVM had previously failed to control infestations of R. microplus ticks were studied. Ticks were collected several months apart in 2013, and the larval immersion test (LIT) was performed on the progeny of the adult females. Concentration-mortality data were subjected to probit analysis. Results: the three populations showed lethal concentrations (LC) 50 and 99 of ≥ 30 ppm and ≥ 400 ppm, respectively. There was no difference observed in the LC at different times of collection for each population studied. Such high values for LC, together with very low regression slopes (≤ 2), indicated a very heterogeneous response to increasing concentrations of IVM, which is common for resistant populations. At two farms, subcutaneous injection with a long-acting formulation of IVM at a dosage of 630 μg/Kg was ineffective at eliminating existing infestations and protecting against reinfestations, confirming farmer suspicions of lost efficacy. Conclusion: epidemiological studies are necessary to assess the current status of resistance to IVM in this region of Colombia, and it is likely that the intensive use of IVM will aggravate this situation in the future.

Antecedentes: en Colombia, el control de la infestación de garrapatas en el ganado se ha realizado casi exclusivamente con acaricidas químicos y es importante determinar el grado de resistencia de las poblaciones de campo de Riphicephalus microplus a ivermectinas (IVM) como el primer paso para diseñar tácticas que aumenten su vida útil y disminuyan la dependencia de los controles químicos. Objetivo: probar el grado de resistencia a IVM. Métodos: se evaluó la resistencia de R. microplus a IVM en tres fincas ganaderas en Antioquia (Colombia) donde se sospechaba que productos con IVM estaban fracasando para controlar infestaciones por garrapatas. Se recolectaron garrapatas con varios meses de diferencia durante el año 2013 y se empleó la prueba de inmersión de larvas (LIT) con la descendencia de las hembras adultas. Los datos de concentraciónmortalidad fueron sometidos a análisis probit. Resultados: los resultados para las tres poblaciones estudiadas mostraron concentraciones letales (LC) 50 y 99 de ≥ 30 ppm y ≥ 400 ppm, respectivamente. No se observó diferencia en las LC obtenidas en diferentes momentos de recogida para cada población estudiada. Los altos valores de LC, junto con pendientes muy bajas en las rectas de regresión (≤ 2), indicaron una respuesta muy heterogénea a concentraciones crecientes de IVM, propio de poblaciones resistentes. En dos de las granjas, la administración de inyecciones subcutáneas con una formulación de acción prolongada de la IVM a dosis de 630 μg/Kg fue incapaz de eliminar las infestaciones y proteger frente a reinfestaciones, confirmando las sospechas de los ganaderos de pérdida de eficacia. Conclusión: estudios epidemiológicos son necesarios para evaluar el estado actual de la resistencia a IVM en esta región de Colombia, y es probable que el uso intensivo de IVM agrave esta situación en el futuro.

Antecedentes: na Colômbia, o controle de infestação com carrapatos em bovinos tem sido realizado quase exclusivamente com acaricidas químicos pelo qual se faz importante para determinar o grau de resistência de populações de campo de Rhipicephalus microplus a uma das drogas antiparasitárias de maior uso no manejo de gado, a ivermectina (IVM), como o primeiro passo para projetar táticas para aumentar a sua vida útil e diminuir a dependência de controles químicos. Objetivo: testar o grau de resistência à ivermectina. Método: foi avaliada a resistência de R. microplus à ivermectina em três fazendas de gado leiteiro localizadas no departamento de Antioquia (Colômbia) com suspeita de que o controle dos carrapatos com a utilização deste produto não estava sendo efetivo. Coletaram-se carrapatos em diferentes meses durante o ano 2013, e foi utilizado o teste de imersão de larvas (LIT) na descendência das fêmeas adultas, como método para detecção da resistência. Os dados de concentração-mortalidade foram submetidos à análise Probit. Resultados: todas as três populações avaliadas mostraram concentrações letais (LC) 50 de ≥ 30 ppm, e LC 99 de ≥ 400 ppm. Não foram observadas diferenças na LC entre as coletas feitas nos diferentes meses, em cada população amostrada. Os altos valores de LC encontrados junto com uma baixa regressão linear (≤ 2), indicam uma resposta muito heterogênea as concentrações crescentes de ivermectina, próprio de populações resistentes. Em duas das fazendas, a administração de injeções subcutâneas de ivermectina com uma formulação de longa ação, em doses de 630 μg/Kg, não foram capazes de eliminar as infestações e proteger contra a reinfestação, confirmando as reclamações dos fazendeiros para a perda de eficácia da droga antiparasitária. Conclusões: os estudos epidemiológicos são necessários para avaliar o estado atual da resistência à ivermectina nesta região da Colômbia, e é provável que o uso intensivo da ivermectina agrave ainda mais esta situação no futuro.