Using weather data to predict the presence of Lucilia spp. on sheep farms in New Zealand.

Flystrike remains an important animal health issue on New Zealand sheep farms. To date no useful predictive tool to assist farmers to develop control options has been available. The aim of this study was to use National Institute of Water and Atmospheric Research (NIWA) virtual climate station data in New Zealand to develop a weather-based model to accurately predict the presence of Lucilia spp. on sheep farms throughout New Zealand. Three LuciTrap® baited fly traps were positioned on each of eight sheep farms throughout New Zealand (5 in the North Island and 3 in the South Island). The traps were put out for both the 2018-2019 and 2019-2020 seasons. They were emptied each week and the flies morphologically identified; with the counts of Lucilia cuprina and L. sericata combined as Lucilia spp. The count data for Lucilia spp. for each week of trapping was transformed into a binary outcome and a generalised linear mixed effects models fitted to the data, with farm as a random effect. The dependent variable was Lucilia spp. flies caught, yes or no, and the independent variables were mean weekly climate variables from the nearest NIWA virtual climate station to that farm. The model was trained on the 2018-2019 catch data and tested on the 2019-2020 catch data. A cut point was identified which maximised the model's ability to correctly predict whether Lucilia spp. were present or not for the 2019-2020 catch data, and the sensitivity, specificity, accuracy, and area under the curve (AUC) of the model calculated. The final model included just 3 significant variables, mean weekly 10 cm soil temperature, mean weekly soil moisture index, and mean weekly wind speed at 10 m. Mean weekly 10 cm soil temperature accounted for 64.7% of the variance explained by the model, mean weekly soil moisture index 34.7% and mean weekly wind speed at 10 m only 0.6%. The results showed that the predictive model had a sensitivity of 0.93 (95% CI = 0.80-0.98) and a specificity of 0.75 (95% CI = 0.62-0.85), using a cut point for the probability of Lucilia spp. being present on farm = 0.383. This model provides New Zealand farmers with a tool which will allow them to know when Lucilia spp. flies will likely be present and thus more accurately plan their interventions to prevent flystrike.

Farm management and husbandry practices associated with spontaneous humeral fractures in New Zealand dairy heifers.

AIMS: To use a farm-based survey to identify characteristics of the New Zealand dairy system associated with the risk of spontaneous humeral fracture in dairy heifers. METHODS: A questionnaire was designed and made available in print and online to collect information from dairy farmers and/or veterinarians, across New Zealand, about the management and nutrition of cows from birth to first lactation. Data were collected from July 2019 to March 2020 from farms that either had recorded (case farms) or not recorded (control farms) cases of humeral fractures in dairy heifers. RESULTS: A total of 68 completed questionnaires were returned, with 35 responses from case farms and 33 responses from control farms. Twenty-six responses (38%) were from the South Island (13 case farms and 13 control farms) and 38 responses (56%) were from the North Island (20 case farms and 18 control farms). For four questionnaires (6%) farm location was not given. Adjusting for the effect of age when calves accessed pasture, case farms had increased odds of having Holstein-Friesian Jersey crossbreed cows as the predominant breed (OR = 9.7; 95% CI = 3.1-36.0; p < 0.001). Adjusting for the effect of breed, allowing calves access to pasture a week later decreased the odds of being a case farm (OR = 0.68; 95% CI = 0.47-0.90; p = 0.006). CONCLUSIONS: Cows being Holstein-Friesian Jersey crossbreed was identified as a possible risk factor associated with spontaneous humeral fracture in dairy heifers in New Zealand. Given the small sample size, the likely multifactorial aetiology for humeral fractures, and the non-randomised survey, this risk factor, and the possible association between age at turn out and herd production with humeral fractures, all require further investigation.

The effect of parenteral vitamin B12 on the growth rate of dairy calves over the summer and autumn on seven farms from the Central Plateau, New Zealand.

AIMS: To investigate the effect of parenteral vitamin B12 supplementation on the growth rate of dairy heifer calves over the summer and autumn on seven farms from the Central Plateau of New Zealand, an area historically associated with low cobalt levels in grazing pasture. METHODS: This was a controlled clinical trial conducted on a convenience sample of seven farms with young female calves randomly assigned to three vitamin B12 treatment groups and followed through a grazing season. Two treatment groups received either monthly SC injections of a short-acting (SA) B12 formulation or 3-monthly injections of a long-acting (LA) B12 formulation and the third group received no treatment (NT). No additional parenteral vitamin B12 was given; however, all calves received additional cobalt (0.04-0.4 mg Co/kg liveweight) in the mineralised anthelmintic drenches given orally every month. Liveweight was recorded in December/January and at the end of the trial in May/June/July depending on farm. Pasture cobalt concentrations (mg/kg DM) were measured every month using 500-g herbage samples from 100-m transects in the area about to be grazed by the trial groups. RESULTS: There was evidence for a difference in growth rate between groups with mean final weight of 228 (95% CI = 212-243) kg for the LA groups, 224 (95% CI = 209-239) kg for the SA groups and 226 (95% CI = 211-241) kg for the NT groups respectively, (global p-value = 0.014). Calves given SA vitamin B12 were 3.77 (95% CI = 0.71-6.82) kg lighter than calves given LA vitamin B12 (p = 0.011). There was no evidence for a change in pasture cobalt concentrations (p = 0.32). CONCLUSIONS AND CLINICAL RELEVANCE: The results of this trial raise the question as to whether the routine use of vitamin B12 supplementation in young cattle from areas traditionally thought to be cobalt deficient is necessary, and further raise the possibility that vitamin B12 supplementation by repeated injection of SA products may negatively impact growth rates.

Downer cows: a reanalysis of an old data set.

AIMS: To compare the performance of two predictive models for the survival of downer cows. METHODS: The first model had been developed in 1987 using a dataset containing missing values, while the second, new model was developed on the same dataset but using modern data imputation and analytical methods. Missing data were imputed using multiple imputation by chained equations and a logistic regression model fitted to the imputed data, with survival or not as the outcome variable. The predictive ability of the model built on the imputed data was contrasted with the original prognostic model by testing them both on a second smaller but complete data set, collected contemporaneously with the development of the original model but from a different region of New Zealand. Sensitivity, specificity, accuracy, and cut point for the two models were calculated. RESULTS: The original 1987 model had a slightly higher accuracy than that of the new one with a sensitivity of 0.85 (95% CI = 0.72-0.94) and a specificity of 0.82 (95% CI = 0.7-0.91), using a cut point for the probability of survival = 0.313. CONCLUSIONS: The original prognostic formula published by Clark et al. in 1987 performed as well as a modern model built on an imputed data set. CLINICAL RELEVANCE: The use of a prognostic test based on the Clark model should remain an important part of the clinical examination of downer cows by New Zealand veterinarians.Abbreviations: AUC: Area under the curve; AST: Aspartate transaminase activity; CK: Creatine phosphokinase activity; GAM: Generalised additive model; NSAID: Non-steroidal-anti-inflammatory drugs; PCV: Packed cell volume.

Longitudinal study of the effect of sporidesmin toxicity on lamb production and serum biochemistry in a flock of 46 Romney ewes using a standardised measure of liver damage.

AIMS: To evaluate the effect of sporidesmin toxicity on production outcomes and serum biochemistry analytes in mixed age Romney ewes, using a standardised measure of liver damage. METHODS: This was a prospective longitudinal study following 46 mixed age Romney ewes from sporidesmin intoxication in April 2019, to slaughter 8 months later. The ewes were blood-sampled up to eight times, with a panel of serum biochemistry tests performed on the final six samples. However, only gamma-glutamyl transferase (GGT) activity was measured in the first two samples collected at the end of sporidesmin intoxication and 2 weeks later. Body condition score, ewe weight and production data were also recorded. Using a standardised liver score, based on histology of liver samples collected at slaughter, ewes were assigned to one of three liver disease categories (LDC); low, middle, and high. These were then used as the outcome or predictor variables for statistical analyses. Finally, two separate decision tree models, using recursive partitioning (RP), were fitted to the biochemistry data and to the GGT data collected at FE outbreak, to predict ewes in the low LDC. RESULTS: There was no evidence of a difference for the effect of LDC on ewe weight (p = 0.86) with ewes, on average, gaining weight to weaning. Weaning percent, lamb rearing percent and ewe flock efficiency were lower in ewes with high LDC, and scanning-to-weaning lamb loss was significantly higher in sheep with high LDC (p = 0.02). Serum activities of GGT and glutamate dehydrogenase and concentration of globulin were significantly lower in sheep with low LDC than in sheep with middle or high LDC (p < 0.05). However, there was no evidence of a difference for the effect of LDC on other biochemistry variables (p > 0.05). The final RP model for the biochemistry data categorised ewes as low LDC if their GGT was <122 IU/L, 3 months after sporidesmin intoxication, or if their GGT was <514 IU/L, <18 days after sporidesmin intoxication. CONCLUSIONS AND CLINICAL RELEVANCE: Sheep with gross and histological evidence of severe sporidesmin-induced liver damage were able to maintain or gain body weight, suggesting that sporidesmin intoxication alone is not causative of poor body condition. Similarly, many of the serum biochemistry tests were not associated with evidence of liver damage. Lamb production was reduced in ewes with evidence of severe liver damage and the decision tree model showed promise as a basis to select ewes for culling.

The role of sheep (Ovis aries) in maintaining Theileria orientalis Ikeda type infection.

Theileria orientalis is a tick‒borne intracellular parasite of red blood cells that causes severe and mild infections in various ruminants worldwide. To date there have been 11 types identified within this species, of which 4 types are presently found in New Zealand cattle. Since 2012, New Zealand has suffered a substantial epidemic of infectious bovine anaemia in both dairy and beef cattle associated with the Ikeda type. The speed at which the disease spread through the North Island suggested that other species could have been involved in transmission. The aim of a series of related experiments was to test the null hypothesis that sheep cannot maintain T. orientalis Ikeda type infection or infect ticks that feed on them. Several studies were conducted over 2 years to address this hypothesis which together showed that sheep can have detectable levels of T. orientalis Ikeda type infection in both the acute and chronic phase and that Haemaphysalis longicornis larvae can become infected when feeding on sheep. No anaemia, weight loss or clinical disease was recorded in the sheep in the acute phase of infection. The levels of infection recorded in the sheep were much lower than those found in cattle, consistent with the sheep being asymptomatic carriers of T. orientalis Ikeda type infection.

Isolates, antimicrobial susceptibility profiles and multidrug resistance of bacteria cultured from samples collected from sheep in New Zealand (2003-2016).

Aim: To describe the common species, antimicrobial susceptibility and multidrug resistance (MDR) of bacteria cultured from samples submitted to veterinary diagnostic laboratories from sheep in New Zealand between 2003 and 2016. Methods: Bacterial culture and antimicrobial susceptibility test data from June 2003 to March 2016 for animals identified as sheep were obtained from two commercial veterinary diagnostic laboratories in New Zealand. Submission information included animal signalment, geographic origin, specimen description, the organisms cultured, and where available, antimicrobial susceptibilities of the isolates. MDR was defined as any isolate with resistance to ≥3 antimicrobial classes. Results: There were 1,971 unique laboratory submissions, yielding 2,188 isolates. Of the 1,971 submissions, the most commonly represented breeds were Romney (933; 47.3%), Romney cross (264; 13.4%), and Coopworth (197; 10.0%), and there were more submissions from females (1,006; 51.0%) than males (184; 9.3%). Most submissions were from Canterbury (549; 27.9%), Southland (471; 23.9%), and Manawatu-Wanganui (272; 13.8%) regions. Other signalment data were inconsistently described. Submitted samples most commonly originated from the gastrointestinal tract (852; 43.2%), faeces (378; 12.1%), or liver (146; 7.4%). Of the 2,188 isolates, 1,771 (80.9%) were identified by species and 247 (11.4%) by genus, with the most common isolates being Salmonella spp. (880; 40.2%), Campylobacter spp. (408; 18.6%), Listeria spp. (140; 6.4%) and Yersinia spp. (113; 5.2%). Susceptibility results were available for 117/2,188 (5.3%) isolates from 51/1,971 (2.6%) submissions. No antimicrobial susceptibility data were available for Salmonella spp., Campylobacter spp., Listeria spp. or Yersinia spp. Overall for the isolates tested, susceptibility to the fluoroquinolones and tetracyclines was greatest, and MDR was found in 24/117 (20.5%) isolates. MDR was a more frequent finding for Enterococcus spp., Bacillus spp., and Proteus mirabilis, but was infrequent in isolates of Staphylococcus aureus, alpha-haemolytic streptococci, Escherichia coli or Enterobacter spp. Conclusions and clinical relevance: This is the first report on antimicrobial susceptibility and MDR for isolates from laboratory submissions from sheep in New Zealand. The low numbers of isolates submitted for antimicrobial susceptibility testing during the period studied mean that these findings provide limited insights into antimicrobial resistance in this population, and highlight the need to address significant gaps in our understanding of why veterinarians do not more frequently submit samples from sheep for bacterial culture and susceptibility testing. Abbreviation: AMR: Antimicrobial resistance; MDR: Multidrug resistance.

Sex Differences in Internalizing Symptoms and Amygdala Functional Connectivity in Neurotypical Youth.

Amygdala resting-state functional connectivity (rsFC) is altered in adolescents with internalizing disorders, though the relationship between rsFC and subclinical symptomatology in neurotypical youth remains unclear. Here we examined whether amygdala rsFC varied across a continuum of internalizing symptoms in 110 typically-developing (TD) youths 8 to 17 years old using functional magnetic resonance imaging (fMRI). We assessed overall internalizing symptoms, as well as anxious-depressed, withdrawn-depressed, and somatic complaints. Given known sex differences in the prevalence of internalizing disorders, we compared connectivity between males and females. As compared to males, females with greater internalizing, anxious-depressed, and somatic symptoms displayed greater connectivity with the cingulate gyrus, insula, and somatosensory cortices. In contrast, males with greater anxious-depressed symptoms demonstrated weaker connectivity with the subcallosal prefrontal cortex. Sex differences in rsFC in relation to symptom severity were evident for the whole amygdala and for two of its subnuclei (centromedial and superficial amygdala). Overall, results suggest that, for females, higher internalizing symptoms are associated with greater rsFC between the amygdala and regions implicated in emotional and somatosensory processing, salience detection, and action selection. Future longitudinal investigations are needed to determine whether this hyperconnectivity may confer resilience to, or pose risk for, the development of internalizing disorders.

The efficacy of toltrazuril treatment for reducing the infection intensity of Theileria orientalis Ikeda type in dairy calves.

The aim of this study was to test the hypothesis that toltrazuril administered at 4 weeks post-turnout reduces the infection intensity of Theileria orientalis Ikeda type in dairy calves and so prevents serious clinical disease in these animals at 2-3 months of age. Two groups of 40 dairy calves on two separate dairy farms in the Waikato were followed for 16 weeks post-turnout onto pasture. On each farm, 20 calves were randomly selected and orally treated with toltrazuril (15 mg/kg) at 4 weeks post-turnout, whilst the remaining 20 calves were left untreated. All 40 calves were blood sampled and weighed at 2, 4, 6, 8, 12, and 16 weeks post-turnout i.e. 6 samplings per calf. A random subset of 10 calves from each treatment group on each farm were faecal sampled at each visit. The blood samples were used to estimate the T. orientalis Ikeda type infection intensity and haematocrit for each calf and the faecal samples were used to estimate the number of coccidia oocysts per gram of faeces. Three linear mixed effects models, to evaluate the effect of toltrazuril treatment on infection intensity, haematocrit (HCT) and weight respectively were fitted to the data. No calves on either farm developed clinical theileriosis or coccidiosis and the three mixed effects linear models, controlling for the effect of farm and days from turnout, showed that there was no effect of treatment on infection intensity (p = 0.81), on HCT (p = 0.99) and on weight gain (p = 0.79). In conclusion, this study showed no evidence supporting the use of toltrazuril to control T. orientalis Ikeda type infection levels and prevent disease.

Effects of Theileria orientalis Ikeda type infection on libido and semen quality of bulls.

There is an epidemic in New Zealand of infectious bovine anaemia associated with Theileria orientalis Ikeda type, an obligate intracellular protozoan parasite. To establish whether T. orientalis Ikeda type infection adversely affects fertility of bulls used for natural mating, a randomised controlled experimental study was conducted. Ten of 17 2-year-old Friesian bulls that had not been previously infected with T. orientalis were infected with T. orientalis Ikeda type and then evaluations occurred during a 20-week period. There were semen and libido evaluations every 2 weeks, starting 4 weeks before the date of infection. In addition, there were blood collections, for haematocrit and infection intensity evaluations, rectal temperatures recorded, and bulls weighed three times weekly for 13 weeks after infection and then once weekly until completion of the study. Physical activity meters were also attached from Days 9-60 and 65-124 post-infection. The ten bulls were successfully infected with T. orientalis Ikeda type and this resulted in a decrease in HCT to about 0.25 by 70 days post-infection. There were no effects of infection on semen quality; however, during the acute phase of infection, when the infection intensity was rapidly increasing, the infected bulls took a longer time period for repeated mounting of females, and were less dominant in the herd social heiracrchy. In conclusion, although the transitory effects on libido could reduce conception rates, the overall effects of T. orientalis Ikeda type infection on bull fertility will probably be little.

Predicting the potential distribution of Amblyomma americanum (Acari: Ixodidae) infestation in New Zealand, using maximum entropy-based ecological niche modelling.

Although currently exotic to New Zealand, the potential geographic distribution of Amblyomma americanum (L.), the lone star tick, was modelled using maximum entropy (MaxEnt). The MaxEnt model was calibrated across the native range of A. americanum in North America using present-day climatic conditions and occurrence data from museum collections. The resulting model was then projected onto New Zealand using both present-day and future climates modelled under two greenhouse gas emission scenarios, representative concentration pathways (RCP) 4.5 (low) and RCP 8.5 (high). Three sets of WorldClim bioclimatic variables were chosen using the jackknife method and tested in MaxEnt using different combinations of model feature class functions and regularization multiplier values. The preferred model was selected based on partial receiver operating characteristic tests, the omission rate and the lowest Akaike information criterion. The final model had four bioclimatic variables, Annual Mean Temperature (BIO1), Annual Precipitation (BIO12), Precipitation Seasonality (BIO15) and Precipitation of Driest Quarter (BIO17), and the projected New Zealand distribution was broadly similar to that of Haemaphysalis longicornis Neumann, New Zealand's only livestock tick, but with a more extensive predicted suitability. The climate change predictions for the year 2050 under both low and high RCP scenarios projected only moderate increases in habitat suitability along the mountain valleys in the South Island. In conclusion, this analysis shows that given the opportunity and license A. americanum could and would successfully establish in New Zealand and could provide another vector for theileriosis organisms.

A longitudinal study of the effect of Theileria orientalis Ikeda type infection on three New Zealand dairy farms naturally infected at pasture.

The aims of this study were to monitor the change in Theileria orientalis Ikeda type infection intensity, haematocrit, milk production and reproduction on three New Zealand spring calving dairy herds, over the 2014-2015 milking season. Three spring calving dairy farms, A, B and C, from high risk (endemically stable), low risk (endemically unstable), and zero risk (disease-free) tick areas respectively were followed through the 2014-2015 milking season. On Farms, A and B, 100 cows were randomly selected at the first visit, and the same cows blood sampled every month thereafter, whilst on Farm C, the whole herd was blood sampled bimonthly (140 cows). Blood samples were tested for haematocrit, by centrifugation, and Ikeda infection intensity, using qPCR. Animals that were Ikeda type PCR positive at the first sampling were described as prevalence cases and cows that were negative at the first sampling and became PCR positive during the sampling period were described as incidence cases. Production and reproduction data were accessed through LIC MINDA® and milk production data was standardised to energy corrected milk (ECM). In addition, the effect of buparvaquone (BPQ) treatment on milk production was estimated on Farm B. The prevalence of infection at the first sampling was 100 % on Farm A, 57 % on Farm B and 26 % on Farm C. The incidence risk of infection over the sampling period on Farms B and C was 25 % and 2 % and the incident rate was 0.026 and 0.002 cases per cow-month respectively. The average infection intensity for prevalence cases on all farms was low throughout the milking season, <7000 Ikeda organisms/µL however, cases of anaemia still occurred. There was no direct effect of infection intensity on milk production or from being a prevalence case compared to an uninfected cow on milk production, across all farms. However, on Farm B there was a loss of 266 kg (95 % CI 82 ̶ 450) ECM (∼20 kg milk solids) for incidence cases and a loss of 458 kg (95 % CI 211 ̶ 710) of ECM for buparvaquone treated cows, compared to uninfected cows. No significant effect of Ikeda infection on reproduction could be shown for Farms B and C, reproductive data for Farm A was not available. The effect of T. orientalis Ikeda type infection on production and reproduction appears to be minimal once animals have passed through the acute phase of infection and reached the chronic, asymptomatic carrier phase of infection.

Bacterial isolates, antimicrobial susceptibility and multidrug resistance in cultures from samples collected from beef and pre-production dairy cattle in New Zealand (2003-2016).

Aims: To describe the common species and the antimicrobial susceptibility of bacteria cultured from samples submitted to commercial veterinary diagnostic laboratories from beef and pre-production dairy cattle between 2003-2016, and to describe the proportion of isolates with multidrug resistance (MDR). Methods: Bacterial culture and antimicrobial susceptibility data from July 2003 to March 2016 were obtained from commercial veterinary diagnostic laboratories in New Zealand. Results were included from samples from beef cattle, irrespective of age or sex, dairy-breed females aged <2 years and dairy-breed males of any age. Submission information provided included the specimen description, the organisms cultured, and the antimicrobial susceptibilities of isolates, if tested. Antimicrobial resistance (AMR) was defined as any isolate not showing susceptibility to an antimicrobial compound and MDR as any isolate showing AMR to ≥3 antimicrobial classes. Results: There were 1,858 unique laboratory submissions, yielding 2,739 isolates. Of these submissions, most were from the Canterbury (389; 21.9%), Manawatu (388; 21.9%) Waikato (231; 12.4%) and Hawke's Bay (136; 7.3%) regions. There were 163 unique species identifications for the 2,739 isolates; the most common were Yersinia pseudotuberculosis (452; 16.5%), Campylobacter jejuni (249; 9.1%), Escherichia coli (230; 8.4%) and Salmonella enterica serovar Typhimurium (143; 5.2%). Only 251/2,739 (9.2%) isolates from 122/1,858 (6.6%) submissions had antimicrobial susceptibility results. There were no sensitivity results for Yersinia spp., and only one each for Salmonella spp., and Campylobacter spp. Amongst the isolates tested, susceptibility to ampicillin was lowest (33/56; 58.9%). Overall, 57/251 (20.7%) isolates tested for antimicrobial susceptibility had MDR, and MDR was most common for Enterococcus spp. (12/17; 71%) and E. coli (13/30; 43%). Conclusions and Clinical Relevance: This is the first report on antimicrobial susceptibility and MDR in New Zealand beef and pre-production dairy cattle. Findings highlight the limited use of bacterial culture and sensitivity testing by veterinarians and deficits in the information accompanying submissions. A national antimicrobial resistance surveillance strategy that specifically includes this population is recommended.

Associations between Theileria orientalis Ikeda type infection and the growth rates and haematocrit of suckled beef calves in the North Island of New Zealand.

AIMS: The principle aim of this study was to examine the association between infection with Theileria orientalis Ikeda type and growth rates of suckled beef calves on four beef farms. In addition, associations between calf sex, sampling time, and individual farm and T. orientalis Ikeda type infection intensity and haematocrit (HCT) were investigated. METHODS: The study was a prospective longitudinal study in which 240 calves from four purposively selected beef farms in the North Island of New Zealand were blood sampled and weighed in late spring, mid-summer and early autumn. Two farms were from high-risk (A and B) and two from low-risk (C and D) tick areas. Blood samples were analysed to determine HCT, and the number of T. orientalis Ikeda type organisms/µL of blood (infection intensity) using a quantitative PCR assay. A calf was defined as infected if >415 organisms/µL were detected in a blood sample. Linear mixed models were used to examine associations between infection intensity, mean daily liveweight gain (MDG), HCT, calf sex and time of sampling on the four farms. RESULTS: On Farms A and B nearly all calves were infected at each sampling time, on Farm C <30% were infected at any sampling and on Farm D infection prevalence increased from 32 to 79% between late spring and early autumn. On Farms C and D, from mid-summer to early autumn, mean MDG was 0.127 (95% CI=0.072-0.183) kg/day less for infected than uninfected calves (p<0.001). On all farms MDG was negatively associated with infection intensity for mid-summer and early autumn sampling times (p=0.037). The relationship between time of sampling and infection intensity varied between farms (p<0.001), and between male and female calves (p=0.018). Females had a higher infection intensity than males at the mid-summer and early autumn samplings. The association between HCT and infection intensity varied with sampling time and farm (p=0.018). There was a strong negative association between infection intensity and HCT at the late spring sampling, but in mid-summer there was no association, and in early autumn only a weak association. CONCLUSIONS AND CLINICAL RELEVANCE: This study has shown that beef farmers in the North Island of New Zealand should be concerned about the welfare effects and economic impacts of T. orientalis Ikeda type infection in suckled beef calves.

The effect of month, farm type and latitude on the level of anaemia associated with Theileria orientalis Ikeda type infection in New Zealand cattle naturally infected at pasture.

Commencing in 2012, an epidemic of infectious bovine anaemia associated with Theileria orientalis Ikeda type has been present in New Zealand. The aims of this study were to analyse the temporal and spatial effects of T. orientalis Ikeda type infection on the sample submission rates and haematocrits of infected cattle over the first two years of the New Zealand epidemic. The data were collected from 30/08/2012 to 28/11/2014 and included all samples that met the case definition for Theileria associated bovine anaemia (TABA) and tested positive for T. orientalis Ikeda type by PCR. The sample submission rates by month and farm type were highly seasonal with dairy farm submissions peaking in September a month before beef farm submissions peaked. A second lesser peak of dairy farm submissions in April was absent for beef farms. A mixed effects model was fitted to the data and showed a significant interaction between farm production type (dairy or beef) and month of sampling (p=0.006) and between latitude and month of sampling (p=0.024). The estimated haematocrit, adjusted for month and latitude, for dairy cattle=0.125 (95%CI 0.121-0.129) and for beef cattle=0.151 (95% CI 0.138-0.165), p<0.0001. This research shows that infected beef animals tend to be less severely affected than dairy animals and that the month of sampling and latitude of the sampled farm have significant and interacting effects on the level of anaemia associated with T. orientalis Ikeda type infection.