Seroprevalence of Neospora caninum and Toxoplasma gondii in black-tailed deer (Odocoileus hemionus columbianus) and mule deer (Odocoileus hemionus hemionus)

The global seroprevalence of Toxoplasma gondii in deer from 1978 to 2019: A systematic review and meta-analysis

Toxoplasma gondii infecting virtually all warm-blooded animals, including humans, is an intracellular protozoan parasite. The immunocompromised patients or pregnant women infected by Toxoplasma usually can cause encephalitis or abortion. Deer are also the important intermediate host of the parasite and people can be infected by ingesting the undercooked venison. Therefore, to raise the attention of the researchers and T. gondii infection on people in deer, we conducted the meta-analysis. All potential publications on the T. gondii infection in deer were retrieved by searching the PubMed, ScienceDirect, Springer- Link, China National Knowledge Infrastructure (CNKI), WanFang, and VIP Chinese Journal Databases. Finally, a total of 48 publications were included. The pooled seroprevalence of T. gondii infection in deer was 22.92% (95% CI 17.89-28.38) calculated by the random effect model. The seroprevalence of T. gondii infection in deer was the lowest in Asia (12.72%, 95% CI 6.29-20.89), and the highest in North America (32.21%, 95% CI 20.32-45.39). The highest point estimate of deer T. gondii in detection method subgroup was using MAT (31.28%, 95% CI 20.15-43.61). The estimated pooled seroprevalence of T. gondii infection in elk (63.50%, 95% CI 50.01-76.01) was higher than other types of deer. Our meta-regression analysis found that the subgroups including region, sampling year, age, climate, and deer species may be the main heterogeneous source in our meta-analysis. It is necessary to monitor the seroprevalence of T. gondii infection in deer at all times. Furthermore, people should be taken to precautions when ingesting the venison by cooking it well before serving to prevent the T. gondii infection via eating venison.

Comparative health assessment of urban and non-urban free-ranging mule deer (Odocoileus hemionus) in southeastern British Columbia, Canada

Background

The provincial wildlife management agency, British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development, performed a translocation to control the urban mule deer (Odocoileus hemionus; uMD) overpopulation and supplement the declining non-urban mule deer (nuMD) population in the Kootenay region, British Columbia, Canada. The objectives of this cross-sectional study were to evaluate the health of the urban and nuMD populations by comparing pathogen exposure, body condition scores (BCS) and pregnancy rates, to characterize the health risks associated with the translocation and to investigate the role of infectious diseases in the decline of the nuMD deer population.

Methods

Two hundred free-ranging mule deer were captured in urban and non-urban environments in the Kootenay region from 2014 to 2017. BCS and morphometric examinations were performed for each deer. Blood samples collected from each deer were tested for exposure to selected pathogens and pregnancy status.

Results

Body condition scores averaged 3.4 on a five-point scale, was greater in nuMD, and significantly differed between years. Antibodies were detected for adenovirus hemorrhagic disease virus (38.4% (uMD 43.7%, nuMD 33.3%)), bluetongue virus (0.6% (uMD 1.2%, nuMD 0%)), bovine respiratory syncytial virus (8.4% (uMD 4.6%, nuMD 12.1%)), bovine viral diarrhea virus (1.1% (uMD 0%, nuMD 2.2%)), bovine parainfluenza-3 virus (27.0% (uMD 27.6%, nuMD 26.4%)), Neospora caninum (22.1% (uMD 24.4%, nuMD 19.7%)) and Toxoplasma gondii (8.2% (uMD 12.3%, nuMD 3.9%)). No antibodies against epizootic hemorrhagic disease virus were detected. Pregnancy rates did not differ between the two deer populations (90.7% (uMD 90.6%, nuMD 90.9%)). Exposure to N. caninum was associated with a reduced probability of being pregnant. uMD were more likely to be exposed to T. gondii than nuMD.

Discussion

Comparison of BCS, pregnancy rates and pathogen exposure of uMD and nuMD showed that the health of the two populations did not significantly differ, suggesting uMD translocations do not pose a severe risk of pathogen transmission between mule deer populations and that these selected pathogens do not factor in the decline of the nuMD population. However, inclusion of additional health indicators and creation of a robust predictive disease model are warranted to further characterize the health of mule deer and the health risks associated with uMD translocations. These results should be considered as part of a formal risk assessment for future uMD translocations in southeastern British Columbia.

Prevalence of Antibodies against Neospora caninum in Père David's Deer ( Elaphurus davidianus ) in Beijing, China

Neospora caninum is an apicomplexan protozoan and causes neuromuscular disorders in canids and abortions in cattle worldwide. We screened sera samples from 49 free-ranging Père David's deer ( Elaphurus davidianus ) in a nature reserve in Beijing, China, for antibodies against N. caninum using indirect fluorescence antibody tests and western blot tests. Antibodies were found in 27% of the deer. Western blot analysis revealed antibody reactivity against immunodominant N. caninum antigens of 16, 25, and 37 kDa in size together with other visible bands.

Serologic, trace element, and fecal parasite survey of free-ranging, female mule deer (Odocoileus hemionus) in eastern Washington, USA

Blood and fecal samples collected from 97 free-ranging mule deer (Odocoileus hemionus), from four distinct herds during the spring of 2000 or 2001 in eastern Washington, US, were tested for exposure to selected pathogens, concentrations of trace elements, and presence of parasites in feces. Antibodies were detected to the following: Leptospira interrogans serovar Bratislava (4%), Leptospira interrogans serovar Canicola (1%), Leptospira interrogans serovar Grippotyphosa (13%), Bovine viral diarrhea virus 1 (57%), Bovine respiratory syncytial virus (71%), Infectious bovine rhinotracheitis virus (51%), Bovine parainfluenza virus 3 (61%), Bluetongue virus (25%), and Epizootic hemorrhagic disease virus (25%); 3 of 63 (5%) samples had antibody to Neospora spp. All samples tested for antibody to Brucella abortus and L. interrogans serovar Icterohaemorrhagiae, L. interrogans serovar Pomona, and L. interrogans serovar Hardjo samples were negative. Trace element concentrations from 97 sera were deficient for selenium (17%), copper (19%), iron (34%), calcium (3%), and phosphorus (2%) compared with thresholds established for domestic livestock. Parasites detected in 97 fecal samples included dorsal-spined larvae (probably Parelaphostrongylus sp.) (40%), abomasal nematode eggs (1%), Capillaria sp. eggs (1%), Nematodirus sp. eggs (26%), Moniezia sp. eggs (1%), and Eimeria sp. (2%).

A review of neosporosis and pathologic findings of Neospora caninum infection in wildlife

Neospora caninum is an apicomplexan parasite that is the etiologic agent of neosporosis, a devastating infectious disease regarded as a major cause of reproductive loss in cattle and neuromuscular disease in dogs worldwide. This protozoan pathogen is maintained in the environment by a heteroxenous life cycle that involves a definitive canid host and a wide range of intermediate hosts. In recent years, a number of wildlife species have been investigated for their possible involvement in the N. caninum life cycle and many have been implicated as intermediate hosts. However, in many instances these studies have utilized serological and molecular techniques to detect infection in clinically normal animals, and investigation of possible associated morbidity, mortality, and pathology has been neglected. As such, the occurrence and importance of Neospora-associated disease in wildlife species are unknown. In order to improve our understanding of the significance of N. caninum infection in nondomestic species, the present review provides an up-to-date summary of clinical neosporosis and N. caninum-associated pathologic lesions in naturally and experimentally infected wildlife species. We provide a list of all free-ranging and captive wildlife species identified with N. caninum infection to date using currently available diagnostic tools. The advantages and disadvantages of diagnostic methods in wildlife are addressed in order to recommend optimal diagnosis of confirming N. caninum infection and neosporosis in nondomestic species. Although current data would suggest that N. caninum infection does not adversely impact wildlife populations, there is a need for greater international uniformity in the diagnosis of N. caninum infection and neosporosis in nondomestic species in order to assess the true consequences of parasite infection.

Neospora caninum and Wildlife

Bovine neosporosis caused by Neospora caninum is among the main causes of abortion in cattle nowadays. At present there is no effective treatment or vaccine. Serological evidence in domestic, wild, and zoo animals indicates that many species have been exposed to this parasite. However, many aspects of the life cycle of N. caninum are unknown and the role of wildlife in the life cycle of N. caninum is still not completely elucidated. In North America, there are data consistent with a sylvatic cycle involving white tailed-deer and canids and in Australia a plausible sylvatic cycle could be occurring between wild dogs and their macropod preys. In Europe, a similar sylvatic cycle has not been established but is very likely. The present review is a comprehensive and up to date summary of the current knowledge on the sylvatic cycle of N. caninum, species affected and their geographical distribution. These findings could have important implications in both sylvatic and domestic cycles since infected wildlife may influence the prevalence of infection in cattle farms in the same areas. Wildlife will need to be taken into account in the control measures to reduce the economical losses associated with this important disease in cattle farms.