The Use of Biological Controls for Vector-borne Diseases: the Case of Guinea Fowl and Lyme Disease

Hundreds of viruses, bacteria, and protozoa require a parasitic arthropod for transmission between vertebrate hosts. The failure of many conventional methods of vector-borne disease control has lead modern research to consider biological control methods. Lyme disease is a potentially debilitating condition that has caused many people to seek an effective means of protecting themselves from ticks; the primary vector of the disease. Reducing the chance of encountering a tick is an effective, and thus popular, mode of protection. Using guinea fowl to eat ticks is a widely accepted biological control method used in backyards; however, no sound scientific research has examined the role of guinea fowl in reducing the risk of Lyme disease. Nymphal, blacklegged ticks pose the greatest risk to human health in the northeastern United States, due to their high infection prevalence and small size. This study assessed what effect, if any, guinea fowl have on the density of nymphal and adult ticks in backyards. This was achieved by determining the difference between the density of ticks in yards that have had guinea fowl for at least one year and nearby yards that served as matched controls. Statistical analyses revealed no significant effect of guinea fowl on nymphal densities (Wilcoxon z-value=1.26, p=0.21) but a significant reduction in adult densities on lawns with guinea fowl (Wilcoxon z-value= 2.03, p=.043). This study poses two possible scenarios for the effective reduction of adult tick abundances by guinea fowl: the Predation Hypothesis and Aggressive Exclusion Hypothesis. There was no apparent correlation between the density of adults and the density of nymphs found in yards. Therefore, although the presence of guinea fowl reduces adult tick numbers, this does not appear to have an effect on nymphal tick abundance, the primary vector for Lyme disease transmission. Based on these findings, guinea fowl are not an effective biological-control for Lyme disease vectors.