**3.** *Baylisascaris procyonis* **in raccoons and Allegheny woodrats: nematode-acerbated mammal decline**

*Ascarids* are host-specific nematodes (order Ascaridida, class Secernentea) that are parasitic in the intestines of various terrestrial vertebrates*.* Adult ascarids live in the

#### *Perspective Chapter: The Potential Role of Nematode Parasites in Wildlife Decline – Evidence... DOI: http://dx.doi.org/10.5772/intechopen.103119*

small intestine of their definitive host and produce eggs which are shed in the feces. Eggs are very resistant to environmental extremes and can remain infective in the environment for many years [19, 20]. Like other ascarids, *B. procyonis* has a direct and indirect life cycle and can cause zoonotic infection in a variety of paratenic hosts [20]. Although raccoon (*Procyon lotor*) is the specific host for the adult worm, there is no obligatory intermediate host. Adult female worms in the small intestines of raccoons collectively shed millions of eggs per day which are passed in the hosts' feces. After being passed, *Baylisascaris* eggs continue to develop and an infectious larva develops in 2–4 weeks. Raccoons become infected by ingesting *B. procyonis* eggs or larva during social feeding or grooming activities. In addition, raccoons may become infected by consuming flesh or droppings of other vertebrates (specifically mammals or birds) that have become infected by this roundworm. *B. procyonis* is common (prevalence rates ~65%) throughout North American wherever raccoons are found. Except for heavy infections, *B. procyonis* causes no disease in their primary host [20].

Although raccoons are the natural host for *B. procyonis*, other mammals and birds can become aberrant intermediate hosts after inadvertently ingesting eggs containing infectious larva. In these aberrant hosts, *B. procyonis* causes severe central nervous system disease that is often fatal. The life history of raccoons may contribute to the inadvertent transmission of *Baylisascaris* to non-raccoon species. Raccoon defecate in common latrines resulting in a high abundance and concentration of *B. procyonis* eggs that remain infectious for months due to their resistance to environmental extremes [19, 20].

Allegheny woodrat is a species of new world rodent that is endemic to the Appalachian mountains of eastern North America [21–23]. A decline in the numbers and range of the Allegheny woodrat was first noticed in the 1960s and the decline was considered severe by the mid-1970s. The species has since been extirpated from New York and Connecticut. Extensive surveys in Pennsylvania have revealed that woodrats have disappeared from approximately one third of their former range there [21]. Similar declines have been noted in Maryland and Ohio. Allegheny woodrat populations remained stable in West Virginia but recent data indicates that populations are declining in that state as well. This rapid decline has led to the species being listed as endangered and/or threatened by states throughout its range and is currently considered a species of conservation interest and protection by the U.S. Forest Service – although it is not listed under the Endangered Species Act [24].

Allegheny woodrats typically occur in rocky areas associated with forested mountain ridges such as cliffs, caves, talus slopes and rocky fissures. The rocky barrens where they den are generally devoid of vegetation with the exception of the occasional tree that manages to survive among the rocks. Active primarily at night, woodrats leave the security of their rocky dens to visit adjacent areas to feed on the available vegetation. They are typically found in talus fields having large sized boulders (greater than 1.2 m in diameter). Vegetative associations include birch (*Betula* spp.)/chestnut oak (*Quercus prinus*) forests, scattered birch, oaks and shrubs with herbaceous plants at the base of slopes.

Allegheny woodrats exhibit behaviors that are typical of a 'pack rat' and, besides food items, woodrats also collect and store various non-food items (e.g., feathers, snail shell, dried leaves, human items) in their rocky dens. The foraging behavior of Allegheny woodrats may increase their susceptibility to encountering *Baylisascaris* in the feces of raccoons. For example, woodrats may forage for and collect seeds present in the dried feces found in raccoon latrines. Woodrats may make repeated visits to these latrine sites, collect seeds, and subsequently store them in their food caches resulting in repeated exposure to the parasite [21, 23].

Exposure to raccoon roundworm is considered one of many factors that act synergistically to cause the decline of this native rodent [23]. At raccoon latrine sites associated with woodrats, published prevalence rates of *B. procyonis* vary from 11% (Indiana), 22% (Maryland), and 33% (Pennsylvania) [22, 25, 26]. Accordingly, at sites where woodrats persist, raccoon roundworm was absent [22]. Furthermore, forest fragmentation and raccoon densities are also lower than at sites where woodrats have been extirpated [26–28]. In New York state, an unsuccessful woodrat reintroduction effort in 1990 was attributed to high prevalence of raccoons and *Baylisascaris* at the reintroduction site [29]. Additionally, in Indiana woodrat translocations failed at one site where the presence of raccoons and *Baylisascaris* was high [27]. However, the distribution of anhelminitic baits reduced levels of roundworm contamination permitting persistence of woodrats at additional translocation sites in Indiana [27].

Woodrat translocations should be considered at formerly-occupied sites if raccoon latrines and *B. procyonis* are removed. Anhelminitic baits can be used to reduce roundworm prevalence rates at these sites and the maintenance of continuous, mature deciduous forested habitat will reduce raccoon densities. Furthermore, protecting sites where woodrats persist from habitat alterations that will attract raccoons is important. A comprehensive regional approach to assessing the prevalence of *B. procyonis* in raccoons and the exposure level to infection in woodrat habitat is necessary. Once prevalence rates are more widely-understood, the feasibility of using anhelminitic approaches in core woodrat areas can be considered. Finally, the effects of human encroachment (highways, urban areas, agriculture) forest fragmentation on raccoon densities and woodrat habitat needs to be better understood [21]. A compilation of resources related to Allegheny woodrats, including the effects of *B. procyonis*, is available at: https://library.delval.edu/allegheny-woodrats/conservation.

### **4. Conclusions**

Here we described two nematode parasites, *Strongyloides robustu*s and *B. procyonis*, relatively common in one mammalian host that contribute to decline in another neighboring mammal species of special conservation concern. Where southern and northern flying squirrels are sympatric, *S. robustus* (commonly found in southern species) appears to contribute to poor health in threatened/endangered northern flying squirrels. Recently, *S. robustus*, also found in the invasive Eastern gray squirrel in Europe, appears to be transmitted to the now threatened Eurasian red squirrel and may contribute to its decline by modifying its behavior and limiting its ability to compete with its congener. Similarly, *B. procyonis* a common roundworm of the raccoon is often contracted by the Allegheny woodrat an inhabitant of rocky habitats on forested mountain ridges of the eastern and central U.S.A. where it feeds on and stores seeds deposited in the feces of raccoons deposited in latrines often associated with woodrat habitat. Now lost from more than a third of their original range, decline of the Allegheny woodrat is attributed largely to the presence of raccoons and this roundworm parasite.

Species distribution changes and range shifts due to climate change and/or human activity will result in the emergence of new species assemblages. Within these new assemblages, species may affect each other directly through predation or competition, or indirectly by habitat alteration or restructuring host-parasite interactions [3]. The role of climate change in restructuring host–parasite interactions through shifts in host ranges is poorly understood [4] but case studies in rodents presented here provide some predictions about the potential conservation challenges that may emerge.

*Perspective Chapter: The Potential Role of Nematode Parasites in Wildlife Decline – Evidence... DOI: http://dx.doi.org/10.5772/intechopen.103119*
