Effect of commercial tannins on parasitic infection and immunity of lambs naturally infected with Haemonchus contortus.

This study aimed to evaluate the effects of different doses of quebracho extract tannins (Schinopsis lorenzii) (EQ) included in the basal diet (DB) on the count of eggs per gram of feces (EPG), count of parasites in the abomasum, hematological, and immunological parameters in lambs naturally infected with Haemonchus contortus. Forty-eight lambs were evaluated for 42 days and divided into four groups (n = 12): CONT- lambs that received DB without EQ supplementation; G1%- DB with EQ at 1% of dry matter intake (DMI) level; G3%- DB with EQ at the 3% of DMI level; G6%- DB with EQ at the 6% DMI level. For EPG counts, feces were collected weekly. For counting abomasal parasites, at the end of the experiment (D42) half of the lambs in each group were slaughtered. For hematological and immunological analysis, venous blood samples were collected at D0, D21, and D42 to perform the erythrocyte count, mean cell volume (MCV), hematocrit, differential leukocyte count, total plasma protein dosage, and serum IgA class anti-H. contortus using an indirect enzyme immunoassay (ELISA). In the EPG count, there was no significant difference (p > 0.05) between the groups compared with the control. Analysis of the abomasal parasite count showed Haemonchus contortus in its entirety; however, there was no significant difference (p > 0.05) in the number of males, females, and total parasites. No differences (p > 0.05) were observed in erythrocyte count, MCV, hematocrit, and total plasma protein. The average total leukocyte, monocyte, eosinophil, and basophil counts showed no difference (p > 0.05). However, the averages of segmented neutrophils in the G1% and G3% groups presented a reduction in the percentage of cells (p < 0.05) between D21 and D42. Regarding the lymphocyte count, a difference was observed in the CONT and G3% groups at D21 and D42 (p < 0.05), when compared to D0. The analyses of the average absorbance of anti-Haemonchus contortus serum IgA showed no difference (p > 0.05), when the groups were analyzed over time or when compared between them. It can be concluded that the inclusion of different doses of tannins from EQ did not alter the parasitological, hematological, and immunological parameters of lambs infected with H. contortus.

Salivary, serum, and abomasal mucus IgA as an immune correlate of protection against Haemonchus contortus infection in naturally infected lambs.

This study aimed to evaluate salivary, serum, and abomasal mucus IgA levels in lambs naturally infected with Haemonchus contortus. Thirty-seven crossbred lambs (½ Texel or ½ Ile de France) with an average age of 193 days were evaluated for 56 days after grazing on a contaminated pasture. Fecal samples were collected every 7 days to evaluate the EPG. Blood and saliva samples were collected for IgA measurement every 14 days. On D56, 29 animals were killed for parasite counting and IgA quantification in the abomasal mucus. Salivary, serum, and abomasal mucus IgA were measured by ELISA using third-stage larvae antigens. Salivary and mucus IgA were not correlated, but D14 salivary IgA correlated with EPG on D28 (r = -0.37) and D56 (r = -0.36); D28 salivary IgA correlated with D49 (r = -0.40) and D56 EPG (r = -0.44). Abomasal mucus IgA negatively correlated with EPG from D28 to D56 (r varied from _0.51 to -0.62) and with the counts of all parasitic stages (-0.60 to -0.67). The lambs were classified as susceptible (S) or resistant (R) according to EPG (D56 EPG and cumulative EPG) or IgA (salivary, serum, and mucus IgA). Based on D56 EPG and cumulative EPG, resistant lambs had higher D14 salivary IgA, mucus IgA, and total worm counts. For evaluations based on IgA levels, the EPG of S and R animals differed, indicating that IgA was an immune correlate of protection against natural infection with Haemonchus sp., mainly in the saliva sample of D14.