Detection of Cryptosporidium spp. and Giardia duodenalis DNA in wild deer in Scotland

Cryptosporidium spp. and Giardia duodenalis are zoonotic pathogens that cause enteric disease in humans and animals. This study aimed to identify the species/assemblages of Cryptosporidium and Giardia duodenalis in Scottish wild deer populations. Faecal samples (n = 990) were collected from across mainland Scotland from red deer, roe deer, sika deer and fallow deer. The oocysts/cysts were concentrated, DNA was extracted and then analysed by PCR (Cryptosporidium SSU-rRNA and Giardia duodenalis β-giardin, glutamate dehydrogenase (gdh), triosephosphate isomerase (tpi) DNA). All positive PCR amplicons were sequenced to determine Cryptosporidium species and Giardia assemblage. Overall, 12.3 % (122/990) of samples were positive for Cryptosporidium and identified C. ryanae (77/122), C. parvum (22/122) and C. ubiquitum (13/122). Rates of Cryptosporidium infection varied significantly (P = 0.009) between the deer species. Cryptosporidium was also significantly (P = 0.001) more likely to be detected in male deer compared to females and in seasons with high rainfall (P = 0.002). Giardia was detected in 7.9 % (76/962) samples, and sequencing identified assemblage A (62/76), assemblage B (4/76), assemblage D (2/76) and assemblage E (5/76). The assemblages of 3/76 positive samples were unidentifiable. Detection of Giardia was significantly higher (P < 0.001) in roe deer than the other deer species. During this study we also demonstrate that deer calves had significantly higher rates of infection for both Cryptosporidium (P = 0.001) and Giardia (P < 0.001), than other age groups. Co-infection with both pathogens was rare (14/962 samples). These findings confirm that wild Scottish deer harbour both Cryptosporidium and Giardia; however, their role in transmission to humans or livestock remains unclear.