Relationship of intestinal histology with the resistance to Trichostrongylus colubriformis infection in three breeds of sheep

Abstract

The study was carried out to evaluate the relationship of inflammatory intestinal cells with the resistance to Trichostrongylus colubriformis infections in three breeds of sheep (Santa Ines, Suffolk and Ile de France), naturally infected. Mast cells, eosinophils, and globule leucocytes were enumerated in intestinal mucosa. Histamine concentration was estimated in intestinal tissue samples and the length of male and female specimens were determined. The three breeds of sheep showed similar cellular response in the small intestine mucosa (P>0.05). There was extensive variation among sheep in the parasitological and inflammatory cell variables, even in lambs of the same breed. In general, animals presenting less inflammatory cells had a larger worm burden, higher fecal egg counts, and larger T. colubriformis worms. The inflammatory cells possibly impaired the parasite's establishment, development, and survival.

Immune response and performance of growing Santa Ines lambs to artificial Trichostrongylus colubriformis infections

“…Most of the lambs had few parasites: 13-1540 nematodes in six animals, representing an establishment of <1.6% of the inoculum, whereas four lambs had a relatively high parasitic load, of 6310-26830 adults specimens. Similar variability was found in male Santa Ines sheep, aged approximately one year and those naturally infected with gastrointestinal nematodes, which also showed an aggregated distribution of parasites with a mean of 4897 T. colubriformis specimens and worm burden ranging from 290 to 31,300 parasites (Amarante et al, 2007). According to Dobson et al (1990a), the variability between host worm burdens increases over the course of infection and the primary mechanism for T. colubriformis adult worm elimination is the rejection by the host.…”

Comparison of two methods for the quantification of gastrointestinal nematode infective larvae from pasture

“…Verschave et al (2015) assessed the same pasture-collection methods for quantifying L3 of bovine gastrointestinal nematodes in Belgium and also did not find significant statistical differences between the methods. Considering the 16 lambs used in each paddock of the experiment, with an average of 6,748 EPG, with 25 kg live weight, and defecating around 5% of their live weight per day (AMARANTE et al, 2007), it can be estimated that approximately 404,880,000 eggs were deposited during the three occupation days. Therefore, the L3 recovery rate in this study was 0.14%, which is a low number despite being higher than those reported by other authors performing this evaluation.…”

“…In addition to determining the herbage availability in the area, with the data obtained by the Random-plot method it is possible to estimate the number of L3 an animal ingests per day. Using the previous example of 1,609 L3 recovered in 74.56 g of DM, a 25-kg animal consuming around 3% of its live weight (DM) in black oat (BERNARDES et al, 2015) is estimated to consume 16,185 L3 daily. It is not possible to infer whether this L3 intake value might compromise the animal production, as there are no literature reports of a limit value after which animal performance would start declining.…”

ALTERAÇÕES CLÍNICAS E LABORATORIAIS COMO INDICADORES PARA O TRATAMENTO ANTI-HELMÍNTICO EM OVINOS EXPERIMENTALMENTE INFECTADOS COM Haemonchus contortus

“…Após o período pré-patente de 21 dias, o OPG nos animais infectados experimentalmente aumentou progressivamente até atingir seu maior valor aos 42 dias de observação, decaindo nas semanas seguintes até o final do experimento. A redução do OPG do grupo infectado a partir 42° dia pode ser justificada pelo aumento de resistência dos animais, o que limita o estabelecimento de larvas infectantes, o crescimento e a fecundidade dos nematoides e pode até mesmo levar à eliminação dos parasitos presentes, como também foi descrito em trabalhos desenvolvidos por Bricarello et al (4) e Amarante et al (6) .…”

“…A patogenia da verminose e o aparecimento de sinais clínicos podem variar de acordo com a idade do hospedeiro, a imunidade adquirida em infecções prévias, o estado nutricional, a intensidade da carga parasitária e as espécies de nematoides envolvidos (2) . Assim, a presença do parasito não significa necessariamente a ocorrência da doença, uma vez que o aumento da resistência desenvolvida pelo animal pode limitar o desenvolvimento ou mesmo levar à eliminação dos parasitos presentes (4)(5)(6) . Em pequenos ruminantes, a intensidade da anemia e da hipoproteinemia são usualmente os indicadores da gravidade das parasitoses gastrintestinais, principalmente as ocasionadas pelo parasito Haemonchus contortus (7) .…”