Effect of Eimeria acervulina infection history on the immune response and transmission in broilers

Abstract

Heterogeneity in exposure to Eimeria spp. of chickens in a flock will result in differences between individual birds in oocyst output and acquired immunity, which subsequently affects transmission of the parasite in the population. The aim of this study was to quantify effects of previous infection of broilers with Eimeria acervulina on immune responses, oocyst output and transmission. A transmission experiment was carried out with pair-wise housed broilers, that differed in infection history. This "infection history" was achieved by establishment of a primary infection by inoculation of birds with 50,000 sporulated E. acervulina oocysts at day 6 of age ("primed"); the other birds did not receive a primary infection ("naïve"). The actual transmission experiment started at day 24 of age: one bird (I) was inoculated with 50,000 sporulated oocysts and was housed together with a non-inoculated contact bird (C). Oocyst excretion and parameters describing transmission, i.e. the number of infected C birds and time passed before start of excretion of C birds, were determined from day 28 to day 50 for six pairs of four different combinations of I and C birds (I-C): naïve-naïve, naïve-primed, primed-naïve and primed-primed. Immune parameters, CD4(+), CD8(+), αβTCR(+) and γδTCR(+) T cells and macrophages in duodenum, were determined in an additional 25 non-primed, non-inoculated control birds, and in the naïve-naïve and naïve-primed groups, each group consisting of 25 pairs. Although the numbers of CD4(+) T cells and γδTCR(+) T cells increased after primary infection, none of the immunological cell types provided an indication of differences in infectivity, susceptibility or transmission between birds. Oocyst output was significantly reduced in primed I and C birds. Transmission was reduced most in the primed-primed group, but nonetheless transmission occurred in all groups. This study also showed that acquired immunity significantly reduced oocyst output after inoculation and contact-infection, but not sufficiently to prevent transmission to contact-exposed birds.

The effects of combiningArtemisia annuaandCurcuma longaethanolic extracts in broilers challenged with infective oocysts ofEimeria acervulinaandE. maxima

“…From this strategy (even compromising the identification of lesions in broiler intestines in accordance with the pre-patent period of the parasites as proposed by Johnson and Reid (1970)), it allowed our group to assess the effects of treatments on intestinal lesions and, at the same time, allow seeders to infect fellow broilers by contact (Velkers et al . 2010) imitating the natural transmission pathway on commercial farms, which was the objective of the current study.…”

“…Broiler seeders were artificially challenged with dual coccidial infections at 8 days of age and euthanized for lesion scoring 9 days post inoculation, allowing sufficient time to contaminate the litter in each pen in accordance with the prepatent period of E. acervulina and E. maxima parasites (Eckert et al 1995). From this strategy (even compromising the identification of lesions in broiler intestines in accordance with the pre-patent period of the parasites as proposed by Johnson and Reid (1970)), it allowed our group to assess the effects of treatments on intestinal lesions and, at the same time, allow seeders to infect fellow broilers by contact (Velkers et al 2010) imitating the natural transmission pathway on commercial farms, which was the objective of the current study.…”

“…Strains of intermediary virulence were obtained in the Laboratory of Molecular Biology of Coccidians, Department of Parasitology, University of Sao Paulo. These broilers were nominated 'seeders' and were raised with contemporary broilers with the aim of transmitting the disease by contact (Velkers et al 2010). Seeders were removed from the pens 9 days post inoculation and harvested (cervical dislocation) for scoring of lesions (n = 5 per treatment) in a strategy adapted from Johnson and Reid (1970) and supported by illustrations provided by Anonymous (1990).…”

Isospora bocamontensis (Protozoa: Apicomplexa) in captive yellow cardinal Gubernatrix cristata (Passeriformes: Emberezidae)

“…A primary infection can reduce significantly the occysts excretion in a subsequent secondary infection. The birds infected naturally by contact have shown that even a low occysts excretion may cause infections by contact, and the level of occysts expelled will depend on the condition of acquired immunity (Velkers et al 2010).…”

Desempenho produtivo e microbiota intestinal de frangos de corte suplementados com ß-ácidos do lúpulo (Humulus lupulus) após desafio com Eimeria acervulina e E. tenella

“…Entre estes mecanimos tem-se a barreira epitelial mucosa, fagócitos e outros leucócitos, citocinas e componentes do sistema complemento (YUN et al, 2000). Todavia, o principal meio de controle da doença é através do uso de drogas anticoccidianas, associada com vacinas vivas atenuadas (VELKERS et al, 2010 GIANNENAS et al, 2003;NAIDOO et al, 2008;LEE et al, 2011;ALMEIDA et al, 2012;KIM et al, 2013 O produto utilizado contendo o β-ácido possui concentração de 30%, ou seja, para obter a dosagem de β-ácido especificado utilizou-se 100, 200, 400 e 800 mg/kg do produto para os tratamentos 3, 4, 5 e 6, respectivamente. As concentrações totais de β-ácido detectado nas dietas experimentais estão apresentadas na Tabela 2.…”