Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2016
Publication Date: 2/1/2017
Citation: Miska, K.B., Fetterer, R.H. 2017. The mRNA expression of amino acid and sugar transporters, aminopeptidase, as well as the di- and tri-peptide transporter PepT1 in the intestines of Eimeria infected broiler chickens. Poultry Science. 1;96(2):465-473. https://doi.org/10.3382/ps/pew303.
Interpretive Summary: Coccidiosis is responsible for causing large economic losses to the poultry industry worldwide. This disease is caused by a single celled parasite Eimeria. Several species of Eimeria are responsible for causing coccidiosis. Eimeria infect gut epithelial cells that line the inside of the intestine and different species of Eimeria are partial to infection of specific portions of the gut. At the height of infection the parasites cause damage to the intestine, resulting in loss of appetite, diarrhea, and sometimes death. The goal of the present study was to determine how three different species of Eimeria affect the expression of molecules involved with breakdown and uptake of nutrients like proteins and sugars. Since Eimeria infection negatively affects weight gain it is likely that it also interferes with nutrient uptake. The results indicate that all three species of Eimeria tested caused a decrease in molecules that are located at the membrane that faces the lumen of the gut and are responsible of uptake of molecules directly from the gastrointestinal tract into the gut epithelial cells, at the height of infection. On the other hand the expression of molecules at the basolateral membrane, through which molecules pass so they can be transported to other organs and tissues depended chiefly on the species of Eimeria used in infection. Little change was observed in Eimeria maxima infected birds over the course of infection, while Eimeria acervulina infection resulted in increased expression at the height of infection. In summary, during Eimeria infection of chickens there is most likely a decrease in the amount of nutrients that can enter the gut epithelium particularly at the height of infection, which may have a negative impact on weight gain. The responses observed at the basolateral membrane which allows nutrients to be transported to other parts of the body are more complex and appear to be species specific however, these responses may limit the nutrients available to the Eimeria infected gut epithelial cells and therefore limiting the Eimeria life cycle.
Technical Abstract: Coccidiosis in chickens is caused by infection of gut epithelial cells with protozoan parasites of the genus Eimeria. This disease causes losses to the poultry industry since infected birds fail to gain weight as rapidly as non-infected birds and efficiency of feed conversion is compromised. For the present study the effect of Eimeria on expression of components of amino acid and sugar uptake mechanisms was determined. Broiler chicks were infected with Eimeria maxima, which infects the jejunum, Eimeria acervulina that infects the duodenum, or Eimeria tenella which infects the ceca. Sections of the jejunum, duodenum, and ceca (depending on species of Eimeria) were taken at several time points between days 0 and 14 post-infection (PI) for mRNA expression analysis. Genes examined included one digestive enzyme, seven peptide and amino acid transporters located on the brush border, eight transporters located at the basolateral surface of the gut epithelium and five sugar transporters. All three Eimeria species examined caused decrease in expression of brush border transporters particularly at days 5-7 PI which corresponds to the time when pathology is greatest. The same pattern was seen in expression of sugar transporters. However, the expression of basolateral transporters differed among species. Eimeria tenella infection resulted in decreased expression of all basolateral transporters, while E. maxima infection caused increased expression of two genes and slight decrease in expression of the remaining five genes. Infection with E. acervulina resulted in increased expression at the height of infection of all but one basolateral transporters. In conclusion, Eimeria infection causes a general decrease in gene expression of sugar transporter and brush border AATs at height of infection. However the expression of basolateral transporters is increased in E. maxima and E. acervulina infected birds. It is possible that decreased expression of brush border transporters in combination with increased expression of basolateral transporter leads to decrease of nutrients available for the parasite thus limiting parasite reproduction.