Experimental infection of calves with Haemonchus placei and Haemonchus contortus: Assessment of parasitological parameters

Abstract

The present study evaluated the viability and possible effects of Haemonchus contortus infections in experimentally prime infected calves, comparing them to infections by Haemonchus placei. Ten male Holstein newborns were used. All calves were individually weighed for subsequent group formation, in which two animals were kept as a control group, inoculated with water (GI); four animals were inoculated with 10,000 third stage (L3) Haemonchus contortus larvae (GII); and the remaining four calves were inoculated with 10,000 third stage (L3) H. placei larvae (GIII). All experimental animals were necropsied on the 42nd day after inoculation. Based on results obtained by the present study, it can be concluded that bovine calves were susceptible to infections by both Haemonchus species (placei and contortus). H. contortus presented an inferior pre-patent period when compared to H. placei. No significant difference (P>0.05) was observed between Haemonchus burdens recovered from both infected groups (GII and GIII). Moreover, H. contortus females maintained an egg production rate similar to H. placei females in young animals, which can contribute to pasture contamination by both Haemonchus species. This could possibly lead to negative reflexes on helminth control based on a mixed pasture with bovines and ovines, especially when it involves younglings.

Establishment of co-infection and hybridization of Haemonchus contortus and Haemonchus placei in sheep

“…A strong host-specificity in which cross-infection is negligible has been reported in the French West Indies (Giudici et al , 1999) and Brazil (Amarante et al , 1997; Silva et al , 2015), where H. contortus primarily infects small ruminants and H. placei infects bovines. However, artificial infections with H. contortus can be established successfully in cattle (Bassetto et al , 2011; Fávero et al , 2016), and with H. placei in sheep (Santos et al , 2014a; Reiniger et al ., 2017). In addition, mixed infections have been reported in livestock production systems in which cattle and small ruminants share the same pasture in different areas of the world, such as West Africa (Jacquiet et al , 1998; Achi et al , 2003), Egypt (Khalafalla et al , 2011), Western Australia (Jabbar et al , 2014) and the United States (Chaudhry et al , 2014).…”

Haemonchosis en una ternera raza Brahman en el trópico alto del Nordeste Antioqueño

“…Estudios experimentales con infecciones establecidas de larvas con la especie H. contortus, han demostrado que el número de larvas capaces de instaurarse y llegar a completar el ciclo es mucho menor en bovinos que en ovinos (7,16 vs 28,8%); por ello se considera a los bovinos mucho más resistentes para dicha especie de Haemonchus que los pequeños rumiantes 13 . Sin embargo, ambas especies de Haemonchus (contortus y placei) son igual de patógenas en terneros por presentar tasas de infección similares de alrededor del 7% 8,9 , y existen reportes que implican al H. contortus en casos de mortalidad en terneros 15,23 .…”

“…Aunque el conteo de huevos por gramo de heces (HPG) ha sido el parámetro más usado en la mayoría de estudios, no se correlacionan bien con la carga parasitaria y un animal con gastroenteritis parasitaria puede estar eliminando desde varios cientos hasta miles de HPG. De igual manera, tampoco se han establecido umbrales de HPG que produzcan perdidas subclínicas por reducción en la ganancia de peso 26 , si bien MEDICINA VETERINARIA Y ZOOTECNIA en un estudio experimental reciente se observó que terneros con cargas moderadas entre 200-700 HPG y que no produjeron alteraciones hematológicas ni clínicas, sí tenían menor ganancia de peso que en los animales no infectados 8,9 . A pesar de no existir evidencias claras para establecer umbrales de HPG, varios autores han establecido niveles arbitrarios para clasificar el grado de infecciones mixtas por trichostrongylidos en: leves (<200 HPG), moderadas (200-700 HPG) y altas (>700 HPG) 20,22 .…”

PCR primers for straightforward differentiation ofHaemonchus contortus, Haemonchus placeiand their hybrids

“…In artificial infections, H. placei and H. contortus establish well in both sheep and cattle hosts (Santos et al ., 2014; Fávero et al ., 2016), but host specificity is evident where cattle and sheep share pastures (Santiago et al ., 1975; Amarante et al ., 1997). However, cross-infections can occur in areas where both parasites are sympatric, a situation that favours the production of hybrids (Hussain et al ., 2014).…”