Currently, the range of tick species that transmit Lyme disease are expanding due to climate change and human alteration of the natural environment. As a result, Lyme disease is a growing threat to those that play golf or work on golf courses since they can provide suitable habitat for ticks.
The Lyme disease bacterium, Borrelia burgdorferi, is spread through the bite of infected ticks. The main species of tick capable of transmitting Lyme disease is in North America is the black-legged tick (Ixodes scapularis or deer tick). Another species capable of Lyme disease transmission is the western black-legged tick (Ixodes pacificus) which is found in western portion of the continent.
The lifecycle of an Ixodes scapularis tick is normally two years. During their life cycle, they move through four stages of life: egg, larva, nymph, and adult. Ticks require a blood meal to progress to each successive stage in their life cycles.
The larvae hatch in spring, have six legs and are the size of a period at the end of a sentence. At this stage the tick is not capable of transmitting Lyme disease since they have not fed on an infected host. Ticks perform a procedure known as questing when awaiting a host to provide a bloodmeal. Questing is a process in which ticks grasp onto leaves or grass by their third and fourth pair of legs and hold their first pair of legs outstretched, waiting for a host to pass by. When a host moves in close vicinity to the questing tick, it quickly uses it front pair of legs to attach upon an unsuspecting victim. Larval ticks will quest near the ground often in leaf litter. The larva then attaches itself to its host which is normally a mouse or ground feeding bird, begins feeding, and over a few days takes its blood meal. If the host was infected with the Lyme disease bacterium from previous tick bites, the larva will very likely become infected as well. After feeding the larva will drop off from their hosts and molt into a nymph.
The nymphs will not start seeking a host to feed upon until following spring or early summer. The eight-legged nymphs are the approximate size of a poppy seed. Nymphs will quest in vegetation such as grasses and leaves less than half of a metre high. Often the new host is a mouse or other small rodent but humans and domestic pets are suitable alternatives. When the tick feeds again, it can transmit the bacterium to its new host or pick up the Lyme disease pathogen for the new host. Ticks in the nymphal stage are more likely to transmit tick-borne pathogens to humans than adult ticks because their small size makes them harder to detect. Once the bloodmeal is complete, the nymph drops off its host and molts into an adult.
The adult black legged ticks have eight legs and are the size of a sesame seed. The adult female tick will actively seek a host in the fall by questing up to a metre above the ground on stems of grass or leaf tips. Deer are the preferred host, but they will seek bloodmeals from larger mammals such as humans, horses or domestic pets. The females require this final bloodmeal to produce eggs. Adult males attach to a mammal host strictly to wait to mate with blood fed females. Since adult males don’t take a blood meal, they do not transmit Lyme disease. The male dies after mating and the female’s life ends after the eggs have been laid. The females that don’t feed in the fall and males that have not mated will overwinter and the females will seek a large mammal to feed upon the following spring.
The risk of acquiring Lyme disease is highly seasonal and individuals that participate in outdoor activities in the vicinity of tick habitats in the spring and early summer months are at greatest risk as this is when nymphs are most active. In addition, adult females that have not received a blood meal the previous fall continue to seek a final blood meal during this timeframe. A second peak risk period of illness occurs in the fall months when the majority of adult female ticks are seeking hosts. These high-risk periods both occur in some of the busiest parts of the golf season.
Ticks rely on their environment to maintain hydrated and as such require humid environments. Preferred habitats on golf courses include forests, forest edges and tall dense grassy areas that receive full or partial shade. These habitats can also be favoured by white-footed mice which are the most efficient host for harbouring Lyme disease bacteria. Ticks that feed on white-footed mice have a higher probability of becoming infected with Lyme bacterium than ticks feeding on other hosts. Scientific studies have noted that an increase in the mice population in one year can be linked to additional human Lyme disease cases the following year.
A key to reducing Lyme disease in humans is to take measures to try to control the white-footed mouse population, and one way to do that is by supporting natural predators by expanding their habitats or keeping exiting habitats intact. Scientists have found that fragmentation of the forested areas into segments smaller than 1-2 hectares is a significant factor in increasing white-footed mice population densities as fragmentation reduces the number and diversity of predators. Designers of new golf courses or existing golf courses that are planning on reducing the area of their manicured turf by adding natural fields, grasses and woodlots should ensure that these new naturalized areas are large enough to promote biodiversity and support the predators (weasels, foxes, owls, hawks, snakes) of the white -footed mice and other small rodents. The Audubon Cooperative Sanctuary Program for Golf Courses has numerous resources to assist in wildlife and habitat management and planning.
Golf course superintendents should consider implementing an integrated tick management (ITM) program to protect patrons and their golf course maintenance staff. Reducing the risk of tick-borne disease transmission is best accomplished through a combination of methods including surveillance, species identification, personal protection measures, landscape management and targeted applications to control ticks.
The cornerstone of a tick management program is surveillance which will determine tick distribution, density and species composition on the golf course property. The two common tools used in tick surveillance are tick drags and carbon dioxide traps. The successful collection ticks will provide insight into which the tick species are present. Ticks can be submitted to an Alberta Health Services (AHS) Environmental Health Office for species identification.
Course maintenance staff as well as golf course patrons should be aware of personal protection measures such as the use of tick repellents, avoiding tick habitats and wearing protective clothing.
Landscape modifications can create an environment unattractive to ticks as they require shaded habitats with high humidity to survive. Raking leaves, trimming shrubs and other low-lying vegetation will assist reducing ground humidity. The use of mulches and xeriscape landscaping techniques can also help reduce tick habitats.
Under ITM, acaricides should be used if other measures are ineffective. The least-toxic materials should be chosen and applied to minimize exposure to humans and all non-target organisms. Botanical compounds or entomopathogenic organisms such as the entomopathogenic fungus, Metarhizium anisopliae should be considered over synthetic pesticides.
Armed with the knowledge of tick life cycles and integrated tick management tools, golf course superintendents should be able to successfully keep ticks under control.