PARASITE PREVALENCE AND COMMUNITY DIVERSITY IN SYMPATRIC AND ALLOPATRIC POPULATIONS OF TWO WOODRAT SPECIES (SIGMODONTINAE: NEOTOMA ) IN CENTRAL CALIFORNIA

Macro-parasites and micro-parasites co-exist in rodent communities but are associated with different community-level parameters

Wildlife species are often heavily parasitized by multiple infections simultaneously. Yet research on sylvatic transmission cycles, tend to focus on host interactions with a single parasite and neglects the influence of co-infections by other pathogens and parasites. Co-infections between macro-parasites and micro-parasites can alter mechanisms that regulate pathogenesis and are important for understanding disease emergence and dynamics. Wildlife rodent hosts in the Lyme disease system are infected with macro-parasites (i.e., ticks and helminths) and micro-parasites (i.e., Borrelia spp.), however, there has not been a study that investigates the interaction of all three parasites (i.e., I. pacificus, Borrelia spp., and helminths) and how these co-infections impact prevalence of micro-parasites. We live-trapped rodents in ten sites in northern California to collect feces, blood, ear tissue, and attached ticks. These samples were used to test for infection status of Borrelia species (i.e., micro-parasite), and describe the burden of ticks and helminths (i.e., macro-parasites). We found that some rodent hosts were co-infected with all three parasites, however, the burden or presence of concurrent macro-parasites were not associated with Borrelia infections. For macro-parasites, we found that tick burdens were positively associated with rodent Shannon diversity while negatively associated with predator diversity, whereas helminth burdens were not significantly associated with any host community metric. Ticks and tick-borne pathogens are associated with rodent host diversity, predator diversity, and abiotic factors. However, it is still unknown what factors helminths are associated with on the community level. Understanding the mechanisms that influence co-infections of multiple types of parasites within and across hosts is an increasingly critical component of characterizing zoonotic disease transmission and maintenance.

PINWORMS ARE ASSOCIATED WITH TAXONOMIC BUT NOT FUNCTIONAL DIFFERENCES IN THE GUT MICROBIOME OF WHITE-THROATED WOODRATS (NEOTOMA ALBIGULA)

Vertebrates rely on their gut microbiome for digestion, and changes to gut microbial communities can impact host health. Past work, primarily in model organisms, has revealed that endoparasites disrupt the gut microbiome. Here, using wild-caught white-throated woodrats (Neotoma albigula), we tested whether naturally acquired parasite infections are associated with different microbiome structure and function. We surveyed wild N. albigula in eastern Utah for gastrointestinal parasites in the spring and fall of 2019, using traditional fecal float methods and testing a PCR-based approach to detect infection. We tested whether the host gut microbiome structure and function differed based on infection with the most prevalent parasite, the pinworm Lamotheoxyuris ackerti. In spring, infected and uninfected animals had significantly different microbiomes, but these differences were not detected in the fall. However, for both sampling periods, infection was associated with differences in particular microbial taxa determined by differential abundance analysis. As N. albigula rely on their microbiomes to digest both fiber and the plant defensive compound oxalate, we compared microbiome function by measuring dry matter digestibility and oxalate intake in infected and uninfected animals. Although we expected infected animals to have reduced fiber degradation and oxalate intake, we found no difference in microbiome function using these assays. This work suggests that parasite effects on the microbiome may be difficult to detect in complex natural systems, and more studies in wild organisms are warranted.

Analysis on the relationship between winter precipitation and the annual variation of horse stomach fly community in arid desert steppe, Northwest China (2007-2019)

Gasterophilus spp. have been found to be widespread in reintroduced Przewalski's horses in the Kalamaili Nature Reserve (Northwest China). However, data on the annual variation in Gasterophilus infections are lacking. To analyze the epidemiological features and determine the cause of the annual variation in Gasterophilus infections, we treated 110 Przewalski's horses with ivermectin and collected Gasterophilus larvae from fecal samples each winter from 2007 to 2019. All 110 Przewalski's horses studied were found to be infected by Gasterophilus spp., and a total of 141 379 larvae were collected. Six species of Gasterophilus were identified with the following prevalence: G. pecorum (100%), G. nasalis (96.36%), G. nigricornis (94.55%), G. haemorrhoidalis (56.36%), G. intestinalis (59.09%), and G. inermis (3.64%). The mean infection intensity of Gasterophilus spp. larvae in Przewalski's horses was 1285 ± 653. G. pecorum (92.96% ± 6.71%) was the most abundant species. The intensity of Gasterophilus spp. (r = –0.561, P < 0.046) was significantly correlated with winter precipitation. Our findings confirmed that, in the Kalamaili Nature Reserve, gasterophilosis is a severe parasitic disease in Przewalski's horses. Winter precipitation at the beginning of the year can indirectly affect the intensity and composition of Gasterophilus spp. in Przewalski's horses at the end of the year. Therefore, the water‐related ecological regulation should be carried out to help reduce the parasite infection of Przewalski's horses.