Morphometric analysis of Psoroptes spp. mites from bighorn sheep, mule deer, cattle, and rabbits

A morphometric study of Psoroptes spp. mites was conducted to address difficulties encountered in species identification and to provide insights into the phylogenetic relationships between mites found on different hosts. A discriminant analysis employing 9 morphologic characters revealed that the lengths of the outer opisthosomal setae and the lateral margins of the opisthosomal knobs were the 2 most important characters for grouping mites according to host species. This analysis clearly separated mites collected from allopatric populations of bighorn sheep, rabbits, and cattle into discrete groups. However, differences were not detected between mites collected from sympatric populations of infested mule deer and bighorn sheep, suggesting that these mites were not host specific and represented a single interbreeding population. Differences also were not detected among mites collected from the ears and body of bighorn sheep and rabbits, demonstrating that the location of mites on a given host should not be used as a primary criterion in species identification.     

The rise and fall of psoroptic scabies in bighorn sheep in the San Andres Mountains, New Mexico

Between 1978 and 1997, a combination of psoroptic scabies (Psoroptes spp.), mountain lion (Puma concolor) predation, and periodic drought reduced a population of native desert bighorn sheep (Ovis canadensis) in the San Andres Mountains (SAM), New Mexico, from >200 individuals to a single ewe. In 1999, this ewe was captured, ensured to be Psoroptes-free, and released back into the SAM. Eleven radio-collared rams were translocated from the Red Rock Wildlife Area (RRWA) in New Mexico into the SAM range and monitored through 2002 to determine whether Psoroptes spp. mites were still in the environment. None of these sentinel rams acquired scabies during this period, and no additional native sheep were found to be present in the range. In 2002, 51 desert bighorn sheep were translocated into the SAM from the Kofa National Wildlife Refuge in Arizona (n = 20) and the RRWA in New Mexico (n = 31). Twenty-one bighorn sheep have died in the SAM since that time, but Psoroptes spp. mites have not been detected on any of these animals, nor have they been found on mule deer (Odocoileus hemionus) sampled since 2000. We conclude that psoroptic scabies is no longer present in the San Andres bighorn sheep population and that psoroptic scabies poses a minimal to nonexistent threat to the persistence of this population at this time.     

Serodiagnostic antibody responses to Psoroptes sp. infestations in bighorn sheep

The antibody responses of bighorn sheep (Ovis canadensis) infected with Psoroptes sp. mites were investigated by enzyme linked immunosorbent assay on western blots of P. cuniculi antigens. Serum from 20 Psoroptes sp.-infested bighorn sheep (O. canadensis mexicana, O. canadensis nelsoni, O. canadensis canadensis) from New Mexico, Nevada, California, and Idaho reacted strongly with mite antigens ranging from 12 to 34 kd. Serum from 35 Psoroptes sp.-free bighorn sheep of unknown tick infestation status and from three Psoroptes sp.-free bighorn sheep infested with Dermacentor hunteri ticks did not react with these antigens. Psoroptes sp.-specific antibody responses were present throughout a 16 mo period in one infected bighorn sheep, but were not detectable 8 mo following successful treatment. These results demonstrate that specific serodiagnosis of Psoroptes sp. infestation is feasible in bighorn sheep and suggest that antibody responses are indicative of current or recent infestation.     

Kinetic ELISA for detection of antibodies to Psoroptes sp. (Acari: Psoroptidae) in bighorn sheep (Ovis canadensis)

A kinetic enzyme-linked immunosorbent assay (ELISA) was developed using antigenic extracts prepared from Psoroptes cuniculi mites and sera from 37 Psoroptes sp.-infested and 43 uninfested bighorn sheep (Ovis canadensis). Serial dilutions of these serum samples, representing 3 bighorn sheep subspecies and 9 geographic areas, gave parallel responses when plotted as log dilution versus log kinetic rate. Therefore, all 80 samples were run at a single dilution (1:100) and positive/negative cutoff values were established as the mean kinetic rate of all negative sera plus either 2, 3, or 4 standard deviations. The resulting ELISA was highly reproducible and accurate with sensitivities and specificities of 100% and 97.7%, 94.6% and 97.7%, and 94.6% and 100%, respectively. This immunoassay will be useful for prospective and retrospective studies assessing the distribution and prevalence of Psoroptes sp. infestations in bighorn sheep.     

Evaluating apparent competition in limiting the recovery of an endangered ungulate

Predation can disproportionately affect endangered prey populations when generalist predators are numerically linked to more abundant primary prey. Apparent competition, the term for this phenomenon, has been increasingly implicated in the declines of endangered prey populations. We examined the potential for apparent competition to limit the recovery of Sierra Nevada bighorn sheep (Ovis canadensis sierrae), an endangered subspecies under the US Endangered Species Act. Using a combination of location, demographic, and habitat data, we assessed whether cougar (Puma concolor) predation on endangered bighorn sheep was a consequence of their winter range overlap with abundant mule deer (Odocoileus hemionus). Consistent with the apparent competition hypothesis, bighorn sheep populations with higher spatial overlap with deer exhibited higher rates of cougar predation which had additive effects on adult survival. Bighorn sheep killed by cougars were primarily located within deer winter ranges, even though those areas constituted only a portion of the bighorn sheep winter ranges. We suspect that variation in sympatry between bighorn sheep and deer populations was largely driven by differences in habitat selection among bighorn sheep herds. Indeed, bighorn sheep herds that experienced the highest rates of predation and the greatest spatial overlap with deer also exhibited the strongest selection for low elevation habitat. Although predator-mediated apparent competition may limit some populations of bighorn sheep, it is not the primary factor limiting all populations, suggesting that the dynamics of different herds are highly idiosyncratic. Management plans for endangered species should consider the spatial distributions of key competitors and predators to reduce the potential for apparent competition to hijack conservation success.     

Exposure to Psoroptes sp. mites is common among bighorn sheep (Ovis canadensis) populations in California.

Sera (n = 806) from 50 populations of bighorn sheep (Ovis canadensis) in California (USA) were evaluated for antibodies to Psoroptes sp. mites using a kinetic enzyme-linked immunosorbent assay (ELISA). Test values for each sample were determined to be either positive or negative at each of two ELISA cutoff values that provided either 100% sensitivity (low cutoff) or 100% specificity (high cutoff), respectively. One hundred sixty-eight (20.8%) sera were seropositive at the low cutoff value, and 87 (10.8%) of these sera also were seropositive at the high cutoff value. Eleven populations were designated as scabies-suspect and 25 populations were designated as scabies-positive because they had at least one seropositive animal at the low and the high cutoff values, respectively. Based on these results, exposure to Psoroptes sp. mites appeared to be widely distributed among bighorn sheep populations from 1980 to 1990 and infested animals may have been present prior to 1980.     

Serological studies on sympatric Barbary sheep and mule deer from Palo Duro Canyon, Texas.

Sera were collected from 12 Barbary sheet (Ammotragus lervia) and 11 mule deer (Odocoileus hemionus) occupying sympatric ranges in Palo Duro Canyon, Texas. These were tested for leptospirosis, brucellosis, bovine virus diarrhea, anaplasmosis, vesicular stomatitis, bluetongue (BT), epizootic hemorrhagic disease (EHD), infectious bovine rhinotracheitis (IBR), and coccidioidomycosis. Serologic reactors were found to IBR in 3 Barbery sheep, BT in 6 Barbary sheep and 6 mule deer and EHD in 3 Barbary sheep and 4 mule deer. Possible ramifications of evidence for these diseases in wild herbivore populations in this area are discussed.     

Experimental infection of some North American wild ruminants and domestic sheep with Mycobacterium paratuberculosis: clinical and bacteriological findings

Mycobacterium paratuberculosis originally isolated from bighorn sheep (Ovis canadensis) with spontaneous paratuberculosis was used to orally inoculate Rocky Mountain elk (Cervus elaphus nelsoni) calves, mule deer (Odocoileus hemionus) fawns, white-tailed deer (Odocoileus virginianus) fawns, bighorn X mouflon (Ovis musimon) hybrid lambs, and domestic lambs. All experimentally exposed animals became infected. During the first year of infection, hybrid and domestic sheep were able to control the infection but infection was progressive in elk and deer. Clinical paratuberculosis occurred only in mule deer.     

Observations on epizootiology and distribution of Elaeophora schneideri in Montana ruminants.

Seventy-four moose, 111 elk, 20 mule deer, 8 white-tailed deer, 26 prong-horn antelope, 42 domestic sheep and 3 bighorn sheep from Montana or northwestern Wyoming were examined post-mortem for evidence of Elaeophora schneideri infection in 1973-74. Fifteen percent of the mule deer and four percent of the moose were positive for adult arterial worms. This constitutes the first report of E. schneideri in mule deer in Montana. No gross signs of blindness or other neurologic disorder were evident in the infected animals. Potential horsefly intermediate hosts collected in the enzootic area included Hybomitra rhombica osburni, H. tetrica, H. metabola, Chrysops noctifer pertinax and Atylotus incisuralis.     

Elaeophorosis in Barbary sheep and mule deer from the Texas Panhandle

Adult Elaeophora schneideri were recovered from the common carotid artery and its branches in 14 of 14 mule deer, Odocoileus hemionus, and 3 of 9 Barbary sheep or aoudads, Ammotragus lervia, from Palo Duro Canyon in the Texas Panhandle. Gross cutaneous lesions attributable to elaeophorosis in the Barbary sheep varied from small circumscribed scars up to 10 cm in diameter usually on the poll or orbital region to extensive proliferative irregular encrustations on the frontal, temporal and orbital regions, sometimes extending to the ears and muzzle. Individual lesions varied from slate-gray scarred areas to brown proliferative edematous and hyperemic encrustations, sometimes with depigmented pustules a few millimeters in diameter. Microscopic lesions ranged from granulation tissue to severe pyogranulomatous reactions with neutrophils, eosinophils, lymphocytes and plasma cells as the primary infiltration. Foreign body giant cells and/or microfilariae were not observed. Microscopic changes in the carotid arteries and their branches were limited to small villous projections on the intimal surface apparently resulting from medial hyperplasia. Cutaneous lesions attributable to elaeophorosis were not observed in mule deer. Histopathologic lesions in the carotid arteries of mule deer were similar to those observed in Barbary sheep. The comparative pathology of elaeophorosis in various hosts is reviewed and discussed in terms of its pathology in Barbary sheep. The potential ramifications of this infection on the expanding aoudad population in the southwestern United States require that elaeophorosis be considered in the management of this species, particularly in areas with sympatric mule deer populations.     

Geographic distribution of the muscle-dwelling nematode Parelaphostrongylus odocoilei in North America, using molecular identification of first-stage larvae

Molecular identification of dorsal-spined larvae (DSL) from fecal samples indicates that the protostrongylid parasite Parelaphostrongylus odocoilei occupies a broader geographic range in western North America than has been previously reported. We analyzed 2,124 fecal samples at 29 locations from thinhorn sheep (Ovis dalli dalli and O. d. stonei), bighorn sheep (Ovis canadensis canadensis and O. c. californiana), mountain goats (Oreamnos americanus), woodland caribou (Rangifer tarandus caribou), mule deer (Odocoileus hemionus hemionus), and black-tailed deer (O. h. columbianus). The DSL were recovered from populations of thinhorn sheep south, but not north, of the Arctic Circle, and they were not recovered from any of the bighorn sheep populations that we examined. In total, DSL were recovered from 20 locations in the United States and Canada (Alaska, Yukon Territory, Northwest Territories, British Columbia, Alberta, and California). The DSL were identified as P. odocoilei by comparing sequences of the second internal transcribed spacer (ITS2) region of ribosomal RNA among 9 protostrongylid species validated by adult comparative morphology. The ITS2 sequences were markedly different between Parelaphostrongylus and other protostrongylid genera. Smaller fixed differences served as diagnostic markers for the 3 species of Parelaphostrongylus. The ITS2 sequences (n = 60) of P. odocoilei were strongly conserved across its broad geographic range from California to Alaska. Polymorphism at 5 nucleotide positions was consistent with multiple copies of the ITS2 within individual specimens of P. odocoilei. This work combines extensive fecal surveys, comparative morphology, and molecular diagnostic techniques to describe comprehensively the host associations and geographic distribution of a parasitic helminth.     

Serologic survey for brucellosis in feral swine, wild ruminants, and black bear of California, 1977 to 1989.

A retrospective analysis of brucellosis serologic testing results in eight wildlife species in California from 1977 to 1989 was done. Samples were collected from 5,398 live-captured or hunter-killed animals and tested by combinations of up to six serologic tests for antibodies to Brucella spp. Twenty-three of 611 (3.8%) feral swine (Sus scrofa), one of 180 (0.6%) black bear (Ursus americanus), one of 355 (0.3%) California mule deer (Odocoileus hemionus californicus), and one of 1,613 (0.06%) blacktail deer (Odocoileus hemionus columbianus) samples were considered reactors. Suspect serologic reactions occurred in three of 619 (0.5%) desert bighorn sheep (Ovis canadensis nelsoni) and one of 355 (0.3%) California mule deer samples. Brucellosis is not considered an important wildlife health problem in California except in feral swine.     

Comparison of Effects of Shed Antler Hunting and Helicopter Surveys on Ungulate Movements and Space Use

Shed antler hunting (i.e., collecting cast cervid antlers) has increased in popularity during the past decade, but little is known about how this recreational activity affects ungulate movements and space use. We placed geographic positioning system (GPS)-collars on 133 female and male bighorn sheep (Ovis canadensis), bison (Bison bison), and mule deer (Odocoileus hemionus) to quantify their movements and space use during shed antler hunts compared with those behaviors during helicopter surveys in Utah, USA, from 2012 to 2015. For each species, we calculated means and 95% confidence intervals for distance moved during 90-minute segments (16 points/day) pre-event (control, 7 consecutive days prior to event), event (1–2 days), and post-event (7 consecutive days after event) for shed antler hunts and helicopter surveys. We also compared use of space for each species during these events. Female bighorn sheep did not increase distance moved or substantially change space use during shed antler hunts and helicopter surveys. Male bighorn sheep increased distance moved 41% on average during shed antler hunts and by 2.02 times during helicopter surveys but did not change space use during those events. Female bison increased distance moved 15% on average during shed antler hunts and 30% during helicopter surveys. Mule deer increased distance moved and altered space use the most during shed antler hunts; females increased distance moved 97%, and 54% of females moved a mean distance of 742 ± 642 (SD) m (range = 9–3,778 m) outside of their home ranges during those hunts for a mean of 9.2 ± 9.4 hours (range = 1.5 to 41 hr). Male mule deer increased distance moved by 2.10 times on average during shed antler hunts, and 82% of males moved a mean distance of 1,264 ± 732 m (range = 131–3,637 m) outside of their home ranges during those hunts for a mean of 12.6 ± 7.6 hours (range = 4.5–33 hr). Our results provide timely information about how legal shed antler hunting affects movements and space use of female and male ungulates, especially mule deer, and can guide the conservation of ungulate populations and their habitat. © 2021 The Wildlife Society.     

Elaeophorosis in bighorn sheep in New Mexico

Two bighorn sheep (Ovis canadensis) in New Mexico (USA) were found to be naturally infected with Elaeophora schneideri. An adult ram examined in 1997 in the Fra Cristobal Mountains had 26 nematodes in the carotid and iliac arteries, and microfilariae were present in the skin, nasal mucosa, brain, and lungs. This ram was markedly debilitated prior to euthanasia and extensive crusty, scabby lesions were observed on its head. In 1998, a yearling ewe found dead adjacent to Watson Mountain near the Gila Wilderness area was found to have 13 nematodes present in its heart. This is the first report of E. schneideri in bighorn sheep, and we suggest that bighorn sheep are susceptible to E. schneideri infection wherever they coexist with mule deer (Odocoileus hemionus hemionus) and appropriate tabanid vectors.     

The feeding behaviour of Psoroptes spp. mites on rabbits and sheep

A scanning electron microscope (SEM) study of the mouthparts of Psoroptes cuniculi from rabbits and P. ovis from sheep established that they are identical in morphology and are adapted for surface feeding rather than piercing the epidermis. Haemoglobin was found in both P. cuniculi and P. ovis on rabbits but not in P. ovis on sheep and it is concluded that the haemoglobin is derived from small haemorrhages on the surface of inflamed rabbit skin. This inflammation is caused by the deposition of antigenic material on the skin which is abraded by the mite mouthparts. The mites feed on the resulting exudate and on other surface material. An immunofluorescent assay revealed that the 2 mite species are antigenically similar.     

Morphological and molecular comparison of host-derived populations of parasitic Psoroptes mites

Infestation by parasitic Psoroptes mites (Acari: Psoroptidae) is an important cause of economic loss and welfare problems in livestock in many areas of the world. At least five species within this genus have been recognized, based on the host infested, the infestation site and differences in length of the opisthosomal setae of adult male mites. Here the integrity of these species is considered by subjecting populations of mites from a range of host species and geographical locations to simultaneous morphological and molecular genetic analyses. Morphological analysis showed that there were significant differences in shape and size between mite populations from different hosts, and that length of the outer opisthosomal setae in males and the homologous seta in females were the most important distinguishing character in adults. However, considerable variation in outer opisthosomal seta length was evident within and between populations of mites, and differences were not clearly related to host-species or geographical origin and did not support the accepted species differences. Molecular characterization using sequence data from the mitochondrial second internal transcribed spacer (ITS-2) region and microsatellite markers found little or no consistent host-related variation between the mite population samples. The results suggest that there is no case for considering the Psoroptes mites from the different hosts examined as separate species and that the morphological variation observed therefore may represent phenotypic adaptation to the local microenvironment on particular species of host.     

Brucellosis in captive Rocky Mountain bighorn sheep (Ovis canadensis) caused by Brucella abortus biovar 4

Nine (four female, five male) captive adult Rocky Mountain bighorn sheep (Ovis canadensis) contracted brucellosis caused by Brucella abortus biovar 4 as a result of natural exposure to an aborted elk (Cervus elaphus) fetus. Clinical signs of infection were orchitis and epididymitis in males and lymphadenitis and placentitis with abortion in females. Gross pathologic findings included enlargement of the testes or epididymides, or both, and yellow caseous abscesses and pyogranulomas of the same. Brucella abortus biovar 4 was cultured in all bighorn sheep from a variety of tissues, including testes/epididymides, mammary gland, and lymph nodes. All bighorn sheep tested were positive on a variety of standard Brucella serologic tests. This is the first report of brucellosis caused by B. abortus in Rocky Mountain bighorn sheep. It also provides evidence that bighorn sheep develop many of the manifestations ascribed to this disease and that infection can occur from natural exposure to an aborted fetus from another species. Wildlife managers responsible for bighorn sheep populations sympatric with Brucella-infected elk or bison (Bison bison) should be cognizant of the possibility of this disease in bighorn sheep.     

Epidemiology of chronic wasting disease in captive white-tailed and mule deer

The natural occurrence of chronic wasting disease (CWD) in a 1993 cohort of captive white-tailed deer (Odocoileus virginianus) afforded the opportunity to describe epidemic dynamics in this species and to compare dynamics with those seen in contemporary cohorts of captive mule deer (O. hemionus) also infected with CWD. The overall incidence of clinical CWD in white-tailed deer was 82% (nine of 11) among individuals that survived >15 mo. Affected white-tailed deer died or were killed because of terminal CWD at age 49-76 mo (x = 59.6 mo, SE = 3.9 mo). Epidemic dynamics of CWD in captive white-tailed deer were similar to dynamics in mule deer cohorts. Incidence of clinical CWD was 57% (4/7) among hand-raised (HR) and 67% (4/6) among dam-raised (DR) mule deer; affected HR mule deer succumbed at 64-86 mo of age (x = 72 mo; SE = 5 mo), and affected DR mule deer died at age 31-58 mo (x = 41.3 mo; SE = 6.1 mo). Sustained horizontal transmission of CWD most plausibly explained epidemic dynamics, but the original source of exposures could not be determined. Apparent differences in mean age at CWD-caused death among these cohorts may be attributable to differences in the timing or intensity of exposure to CWD, and these factors appear to be more likely to influence epidemic dynamics than species differences. It follows that CWD epidemic dynamics in sympatric, free-ranging white-tailed and mule deer sharing habitats in western North American ranges also may be similar.