Investigation of Toxoplasma gondii and association with early pregnancy and abortion rates in New Zealand farmed red deer (Cervus elaphus).

This study tested for association between Toxoplasma gondii and pregnancy and abortion to investigate sub-optimal reproduction in farmed red deer (Cervus elaphus). Sera from a sub-sample (n = 2304) of pregnant and non-pregnant hinds in early gestation at first pregnancy scan (scan 1) and approximately at the end of second trimester at second pregnancy scan (scan 2) were tested for T. gondii antibodies using a validated ELISA. Foetuses and/or uteri from pregnant, non-pregnant, and aborting hinds at scan 1, scan 2, or weaning were tested for T. gondii DNA by nested PCR. At scan 1, 31.1% of 861 rising two-year-old (R2) and 28.3% of 357 mixed-aged (MA, ≥ 2 years) hinds were sero-positive. There was no association between scan 1 serology and non-pregnancy at animal (R2, p = 0.05 and MA, p = 0.43) or herd level (R2, p = 0.37). Toxoplasma gondii DNA was detected in 3/18 placenta and 4/18 foetal brains from aborting R2 hinds and 15/157 R2 and 3/21 MA uteri from non-pregnant hinds at scan 1. At scan 2, sero-prevalence was higher (odds ratio = 1.6, 95% CI = 1.04-2.48) in aborted (34.3% of 268) than in non-aborted (23.5% of 446) R2 hinds (p = 0.03) and 7.9% of abortions between scans were attributable to T. gondii exposure. Within-herd sero-prevalence at scan 2 was positively associated with daily abortion rate in R2 herds with aborted hinds (p < 0.001) but not in MA herds (p = 0.07). Toxoplasma gondii DNA was detected in 27/169 uteri, 2/20 cotyledons, and 1/5 foetal brains from aborted hinds at scan 2 and in uteri from 5/33 hinds not rearing a calf to weaning. Toxoplasma gondii RFLP genotyping of five loci revealed a unique type I/III genotype pattern, TgRDNZ1, in a foetal brain sample, not been previously reported in deer. These findings provide serological and molecular evidence that T. gondii infection is associated with abortion in red deer, possibly in all three trimesters.

Pregnancy and mid-term abortion rates in farmed red deer in New Zealand.

This paper describes pregnancy and mid-term abortion rate data from an investigation of sub-optimal reproductive performance in New Zealand farmed red deer. For 2 years, 87 yearling (YL) and 71 mixed-age adult (MA) herds from 85 farms were observed with 15 YL and seven MA herds observed both years. Hinds were pregnancy diagnosed using ultrasonography in the late autumn-early winter (PD1) and again late winter-early spring (PD2) and mid-term daily abortion rates (DAR) were calculated. Overall, 85.8% of 22,130YL (range, 7.0%-100% between herds) and 93.3% of 36,223 MA hinds (range, 39.8%-100% between herds) were pregnant at PD1. The mean interval between ultrasonic assessments was 90 and 87 days in YL and MA herds, respectively. Mid-term abortions occurred in 305 (2.8%) hinds from 60 (73%) YL herds and 92 (1.2%) hinds from 36 (61%) MA herds. The mean mid-term DAR, was greater (P = 0.009) in YL (mean 0.043%, range 0.005%-0.213%, 95% CI = 0.034-0.053) than MA herds (mean 0.025%, range 0.007%-0.101%, 95% CI = 0.018-0.032). In herds with hinds that aborted, the mean DAR was greater in small than large YL herds (0.055% compared with 0.033%, P = 0.023), but not MA herds. At PD1, 46 YL and 12 MA hinds had ultrasonographic evidence of abortions from 22 herds. This, combined with the 1.2% to 7.1% foetal loss in three herds pregnancy diagnosed earlier than the usual PD1 date as a pilot to test for earlier abortion, supports that abortion can occur prior to normal pregnancy assessment dates, contributing to sub-optimal pregnancy rates. Abortion rates were not consistent within herd between years for either YL or MA herds. Thus, early and mid-term abortion is prevalent in New Zealand farmed deer constituting a significant production cost, warranting further investigation into causation.

Evaluation of Western blot, ELISA and latex agglutination tests to detect Toxoplasma gondii serum antibodies in farmed red deer.

Abortion due to Toxoplasma gondii has been suspected in New Zealand farmed red deer. However, knowledge around the epidemiology and prevalence of T. gondii in farmed red deer is limited. The aim of this study was to firstly, assess the sensitivity and specificity of two commercially available assays, ELISA and latex agglutination test (LAT), for use in deer and secondly, to estimate the sero-prevalence of T. gondii in red deer. A total of 252 sera from rising 2-year-old and adult hinds from 17 New Zealand red deer herds at early and late pregnancy scanning and from known aborted and/or non-aborted hinds were tested for the presence of T. gondii antibodies. Each assays' sensitivity and specificity was evaluated by both the Western Blot (WB) as a gold standard method and Bayesian latent class (BLC) analysis in the absence of a gold standard. The sensitivity and specificity for WB were 95.8% (95% credible interval: 89.5-99.2%) and 95.1% (95% credible interval: 90.6-98.1%), respectively. For the LAT at the manufacturer's recommended ≥1:32 cut-off titre, the sensitivity (88.7%, 95% credible interval: 80.8-94.7%) and specificity (74.3%, 95% credible interval: 67.5-80.5%) were lower and higher than the sensitivity (76.2%, 95% credible interval: 66.7-84.5%) and specificity (89.7%, 95% credible interval: 84.5-93.9%) at a ≥1:64 cut-off, using (BLC) analysis. Sensitivity and specificity of the LAT at cut-off titre of 1:32 were estimated to be 84.4% (95% CI: 74.9-90.9%) and 73.5% (95% CI: 65.8-79.9%) against WB. The LAT had better agreement with WB at cut-off titre of ≥1:64 than ≥1:32 (Kappa=0.63 vs 0.54). At optimised cut-off S/P of 15.5%, the sensitivity (98.8%, 95% credible interval 96.1-99.8%) and specificity (92.8%, 95% credible interval 88.9-95.7%) of the ELISA were higher and lower, respectively, than the sensitivity (85.1%, 95% credible interval 76.2-91.9%) and specificity (98.5%, 95% credible interval 96.9-99.4%) at manufacturer's cut-off S/P of 30%, from BLC analysis. The sensitivity and specificity of ELISA at S/P cut-off of 15.5% was 91.1% (95% CI: 83.2-96.1%) and 90.7% (95% CI: 85.2-94.7%), respectively, when assessed against WB. The sero-prevalence from ELISA and LAT, at cut-off of S/P 15.5% and ≥1:64, respectively, was not significantly different to that from WB (McNemar's Chi-square p=0.21 for ELISA and p=0.28 for LAT).