The influence of orally administered short chain fatty acids on intestinal histopathological changes and intensity of Trichinella spiralis infection in mice

The influence of short chain fatty acids (SCFA) on histopathological changes in the small intestine and the intensity of invasion of T. spiralis in mice were investigated in this study. The animals were infected with doses of 500 and 250 T. spiralis larvae per mouse. A SCFA solution containing acetic, propionic and butyric acid (30 : 15 : 20mM) was administered orally to the mice starting from the 5^th day before infection to the 20^th day after infection (day). Fragments of the jejunum collected during dissection on the 7th and 10th day were used to prepare specimens to assess the histopathological changes. In the infected animals, the intestinal trichinellae were counted on the 7^th and 10^th day, while on the 42^nd day the muscle larvae number were determined. The strongest host reaction in the intestine was observed on the 7^th day at a dose of T. spiralis 500 larvae, and on the 10^th day at a dose of 250 larvae. Numerous inflammatory infiltrations, strong shortening of the intestinal villi, extension of the intestinal crypts, and the lowest ratio of the villi length to the intestinal crypts depth were observed. The ratio was 1.3 ± 0.3 on the 7^th day at a dose of 500 larvae, and on the 10^th day, at dose of 250 larvae the ratio reached 1.5 ± 0.5. Both values differed significantly from the control group: 3.3 ± 0.5 (P < 0.01). Administration of SCFA to the animals infected with T. spiralis caused remission of local histopathological changes resulting from the presence of the parasite in the small intestine after the mentioned periods. This manifested as limited villi shortening and reduced deepening of intestinal crypts. At the higher infectious dose, in animals receiving the acid solution, on the 7^th day the intestinal villi were considerably longer (356 µm ± 35) than in the group infected with T. spiralis but not treated with the acids (279 µm ± 57; P < 0.01). At a lower dose of parasites, on the 10^th day these values were 339 µm ± 88 and 306 µm ± 47 respectively and the observed differences were not statistically significant. The solution of SCFA also caused a decrease in the numbers of mature parasites in the intestine and the muscle larvae at a dose of 500 larvae/mouse. In animals receiving the SCFA, 24 050 ± 10 415 larvae were observed in muscles, while in the infected mice, which did not receive the acids, 32 875 ± 16 762 larvae were detected (P < 0.05). An increase in the intensity of infection accelerated the rate of host reaction to the presence of T. spiralis in the intestines (self-cure). To summarize, the administered solution of short chain fatty acids alleviated the formation of histopathological changes in the intestine in response to the parasite's presence, and lowered the intensity of T. spiralis invasion after infection with a higher dose of larvae.