Neonicotinoid insecticides exhibit a similarity to nicotine in that they activate nicotinic acetylcholine receptors (nAChRs). In immune cells, activation of this nAChRs signaling leads to immunosuppression. Previous studies have provided evidence that neonicotinoids, when ingested by humans, are absorbed by the intestine and travel to other organs.
A team from the University of Illinois Urbana-Champaign thus sought to investigate how ingestion of such insecticides might affect the body’s immune response to viral infection. Their recent findings based on a livestock model are published in Scientific Reports.
The team introduced imidacloprid (IMI) at a dose of 5 mg/kg/day into the diet of piglets. IMI is a neonicotinoid used in over 120 countries, making it one of the most commonly used insecticides in the world. Randomized groups of piglets were then infected with the reproductive and respiratory syndrome virus (PRRSV).
Among the initial findings, the team found that PRRSV infection, in general, caused a sickness behavior and fever. However, those with an IMI-supplemented diet also exhibited reduced body weight and signs of hypothermia. The body’s absorption of IMI was confirmed by LC-MS/MS analysis of urine samples.
From ELISA analysis on blood serum samples, the team found an increase in circulating IL-10 cytokines in animals fed IMI that were in both PRRSV-infected and -non-infected groups. However, there was no significant interaction between PRRSV and IMI. Similarly, flow cytometric analyses showed that while viral infection briefly increased circulating leukocyte populations, IMI treatment had little effect.
Viral RNA were then measured from lung, blood and spleen tissue samples to determine effects on viral replication. qRT-PCR results showed that viral RNA levels from piglets supplemented with IMI displayed a somewhat strong trend of increasing in the spleen.
The team concluded in their paper: “Our data suggests that dietary supplementation of IMI during PRRSV infection of piglets does not alter the percentage of circulating leukocytes, However, daily treatment affected rectal temperatures and body weights in piglets. Furthermore, IMI treatment increased circulating IL-10 levels, virus-specific antibody titers and showed a statistical trend toward promoting PRRSV dissemination.”