The eosinophil leucocyte, a phenotypic marker of resistance to nematode parasites, is associated with calm behaviour in sheep

Abstract

The hypothesis that behaviour in sheep is influenced by resistance to infections with Trichostrongylus colubriformis and Haemonchus contortus was explored. Sheep were assessed phenotypically as resistant and susceptible in four ways and thereafter, the effect of resistance on several behavioural traits was measured in an arena test. The behavioural parameters recorded for each sheep were: approach/avoidance distance; travel; number of moves; and spread. Four phenotypic groups of sheep were set up each with two subgroups: ovine lymphocyte antigen (OLA) type (subgroups SY1a type vs other types); blood eosinophil leucocyte counts (high vs low); T. colubriformis and H. contortus serum antibodies (high vs low titres) and faecal egg count (FEC) (high vs low). Only the behavioural comparison between sheep with high versus low eosinophil leucocyte count showed consistent differences that were statistically significant, although other comparisons favoured associations between OLA type SY1a, low FEC and reduced approach/avoidance distance and/or locomotor behaviour. The eosinophil leucocyte association was established on two non-overlapping test populations of sheep, with mean eosinophil leucocyte counts of 3.19 x 10(5)/mL blood for high and 0.83 x 10(5)/mL blood for low subgroups; results were reproduced on five separate occasions over 6 weeks to detect differences as approach/avoidance distance (P < 0.01), travel (P < 0.01), number of moves (P < 0.01), and spread (P < 0.05). High eosinophilia correlated with low FEC for the infected sheep, which identified sheep that were resistant to parasites. We concluded, therefore, that the resistant sheep were more at ease with the environment of the test than were the sheep with low eosinophil leucocyte counts. The strong association between high eosinophil leucocyte counts and behaviour is consistent with other reports which suggest that retention of normal levels of circulating eosinophil leucocytes is associated with resistance to stress.

Adaptation to organic rearing system of eight different chicken genotypes: behaviour, welfare and performance

“…Moreover, eosinophils play a major phagocytes role in the defence against parasites (Glick et al 1964). Retention of normal levels of circulating eosinophils is associated with resistance to stress (Woolaston et al 1996;Hohenhaus et al 1998), and changes in blood eosinophils appear as a genotypic or phenotypic hallmark of stress reactions (Malyshev et al 1993;Hohenhaus et al 1998). Their hypothesis is consistent with the present findings that eosinophilia was exhibited in the L, A and CL birds, and not in K, NN and R birds.…”

Intranasal Immunization of Lambs with Serine/Threonine Phosphatase 2A against Gastrointestinal Nematodes

“…In spite of the wide variations found, the immunized lambs had significantly higher levels than all the other groups on days 70 (G2 and G3, P Ͻ 0.05; G1, P Ͻ 0.01), 84 (P Ͻ 0.05), and 97 (G3 and G4, P Ͻ 0.05; G2, P Ͻ 0.01) postimmunization. A rise in eosinophil counts is considered to be a distinct characteristic of helminth infection (57), and eosinophilia has in fact been related to the protection of lambs (58)(59)(60), although this response is variable (61). The absence of clinical signs and notable hematological variations could be related to the moderate infective dose administered.…”

Avaliação do quadro eritrocitário e da repercussão do estado anêmico no leucograma de caprinos com verminose gastrintestinal

“…Correlacionou-se a ocorrência do aumento do número de eosinófilos circulantes com baixos valores de opg nas fezes de ovinos e relacionou-se esse fenômeno com maior resistência animal a infecção parasitária (Hohenhaus et al 1998). …”