Influence of formic acid on the vitality of Strongyloides papillosus

Abstract

Formic acid (methanoic acid, HCOOH) is an organic compound which belongs to saturated monobasic acids. In natural conditions, it is secreted from the glands of ants, and also extracted from the leaves of stinging nettles. It is soluble in water in any proportions, which makes it practical to use for making aquatic solutions. It is broadly used as a preservative in the food industry – Е236 food additive (Codex Alimentarius), as a bactericide in medicine and veterinary medicine, and is also used against agricultural pest species of insects and mites. The in vitro and in vivo experiments revealed the anthelmintic properties of the acid against Strongyloides papillosus nematodes, parasites of the gastrointestinal tract of Ruminantia and rabbits. In the conditions of in vitro, 100% of (L1, L2, L3) nematode larvae died from a 1% solution of formic acid (10 g/l) after 24 hours exposure. When exposed to less strong concentrations of the acid (1, 0.1, 0.01, 0.001 g/l), vital forms of L3 S. papillosus were found. Non-invasive stages (L1, L2) are less resistant to the impact of the acid – death of 100% of the larvae was observed under the impact of 0.1% solution and up to 60% of larvae died at 0.01% solution of formic acid in the same conditions. LD50 for L3 invasive larvae of S. papillosus equaled 0.47%, and 0.0076% for L1, L2 non-invasive larvae of S. papillosus. In the conditions of in vivo experiment (with guinea pigs), the effective dose of formic acid was 0.4% ml/kg of the animal`s body weight. The results of the coproscopy after the treatment demonstrated absence of the helminth larvae in the feces of the laboratory animals during 10 days and their occurrence only on days 15–20 with a low intensity (90 larvae/g of feces on average). During an external examination of the corpses of the animals of the experimental group, no pathological changes were found. The intestine, the heart, the lungs and the liver of the animals from this group had no macroscopic changes – they were of natural colour and size. The hepatocytes looked normal and the structure of the liver lobes was maintained. In the tissues of the liver of the animals from the experimental and control groups, we found processes of passive congestion, and an insignificant degree of signs of hepatic steatosis.