Studies of Northern Fowl Mite Host-Parasite Interactions and Evaluation of Novel Control Strategies in Poultry
Northern fowl mites (Ornithonyssus sylviarum) are the most common and economically important ectoparasites in US laying hen flocks. Mites are permanent ectoparasites and cause damage to birds via blood feeding. Once in a flock, they can be very difficult to eradicate from a property. Mite control has traditionally relied on chemical sprays directed at high pressure underneath the birds and into the vent region where mites live; these applications are most effective when birds are held in battery cages. However in recent years animal welfare concerns and consumer demand has affected how laying hens are housed. The transition to furnished-cage or cage-free production systems will require novel control techniques to achieve ectoparasite control. I investigated possibilities for ectoparasite control that would be effective in alternative poultry housing.
Breeding for parasite resistance is an attractive control method. Chickens develop resistance to the northern fowl mite (NFM) and this is under at least some genetic control. I tested whether the haplotype conferring NFM resistance had any effect on chicken resting metabolism (energy expenditure), physiology, or economic performance. Bird haplotype did not affect hen metabolism or production parameters. NFM infestations negatively affected economic performance.
Dustboxes have been shown to effectively decrease mite populations in cage-free flock when insecticidal dusts are used in combination with sand. I tested whether dustboxes with sand and diatomaceous earth could keep mites below economic thresholds before mite levels became damaging. When dustboxes were present in a flock, mite levels were on average kept below economic threshold regardless of percent of the flock that dustbathed.
Sulfur dust is effective for NFM control in very low doses, though it is not universally approved for organic use. I tested whether sulfur deployed in a dust bag would be effective in caged (non-organic) flocks and if the placement of the bag affected efficacy. Hanging dust bags offered the best NFM control.
Backyard chicken flocks are a growing trend in this country, and nothing is currently know about ectoparasite diversity on these birds. I surveyed 100 birds on 20 properties in southern California. Greater diversity was found on backyard flocks than on commercial birds.