Anthelmintic resistance and management of nematode parasites on beef cattle-rearing farms in the North Island of New Zealand

AIM: To provide information on current farmers’ opinions and farming practices thought to be related to anthelmintic resistance, and to test for associations between the presence of anthelmintic resistance and management practices on beef cattle- rearing farms in the North Island of New Zealand.

METHODS: A study using an interview-based questionnaire about management of internal parasites was conducted on 62 beef cattle-rearing farms in the North Island of New Zealand, using case-control analyses to test for associations between management practices and the presence or absence of resistance to ivermectin or albendazole. Resistance was inferred from faecal nematode egg count (FEC) reduction (FECR) tests (FECRTs) when there was <90% reduction in FEC 7-10 days after treatment of calves <12 months of age.

RESULTS: Of the 59 farmers who completed the questionnaire, most (n=40) ranked parasites highly, and at about the same level as quality and quantity of feed, as important production-limiting factors for their enterprises. In contrast, anthelmintic resistance was not perceived to be a problem on 13 farms, and its importance was rated low on 24, moderate on 15, and high on only six farms. Despite all farms having planned parasite control programmes, there was heavy reliance on clinical signs of parasitism to determine frequency of treatments. About one in three farmers with beef breeder cows routinely treated their calves at marking, one in five treated mixed-age cows, and almost half treated rising 2-year-old cows before calving. One in four farmers used anthelmintics on calves on 8–12 occasions in their first year of life. Co-grazing with other species was rare, but follow-on grazing within 3 months after older cattle or sheep was common. On most farms, grazing cattle was restricted to part of the farm, a finding with implications for parasite control and persistence of larvae in refugia. Macrocyclic lactone (ML) anthelmintics or their combinations with other action families were currently, and for the past 5 years, used more frequently than benzimidazoles and levamisole, and benzimidazole-levami- sole combinations. The prevalence of resistance to ivermectin was high (82%) and no plausible model of associations could be constructed from the data. The prevalence of resistance to albendazole was 60%, and the risk of resistance increased as the number of rising 1-year-old cattle present mid-winter increased, and decreased as the number of breeding cows >2 years old present mid-winter increased.

CONCLUSION: It is clear that in practice anthelmintic resistance is a secondary consideration to obtaining productivity advantages from the use of anthelmintics in beef cattle. Farmers’ opinions were divided on many issues and the overall impres- sion was of confused and diverse thinking regarding the principles of the use of anthelmintics. The overall outlook regarding anthelmintic resistance in cattle is bleak unless the need for integrated and long-term research activities is acted upon soon.     

Diagnosis of laryngeal dysplasia in five horses using magnetic resonance imaging and ultrasonography

Reasons for performing study: Laryngeal dysplasia due to suspected maldevelopment of the fourth branchial arch has been reported previously in the horse and has been associated with rostral displacement of the palatopharyngeal arch and/or right laryngeal dysfunction. These studies all described the endoscopic and/or anatomical post mortem identification of the disease, but ultrasonography or magnetic resonance imaging (MRI) of this disease have not been described. Hypothesis: MRI and ultrasound findings accurately reflect the anatomical features of presumptive fourth branchial arch abnormality and allow accurate ante mortem diagnosis of this condition and, therefore, appropriate management. Methods: Between February 2008 and January 2009, all horses examined at Rood and Riddle Equine Hospital diagnosed with rostral displacement of the palatopharyngeal arch and/or right laryngeal dysfunction using upper airway endoscopy (n = 5) underwent ultrasonography and MRI of the laryngeal region. Results: All 5 horses that met the inclusion criteria were identified and all underwent laryngeal MRI and ultrasound examinations. Features consistent with laryngeal dysplasia, including lack of the cricothyroid articulation, dorsal extension of the thyroid cartilage lamina, and absence or hypoplasia of the cricopharyngeus muscle, were seen in all cases using both types of imaging. Conclusions and potential relevance: MRI and ultrasonography permit definitive premortem diagnosis of laryngeal dysplasia. Upper airway abnormalities identified using endoscopy can be more fully characterised using MRI and ultrasonography allowing more appropriate recommendations to be made. Preoperative imaging may also prevent inappropriate surgical intervention.     

Equine amnionitis and fetal loss: The case definition for an unrecognised cause of abortion in mares

A series of abortions occurred in mares in New South Wales during 2004 that involved similar and unusual findings on post mortem examination of aborted fetuses and fetal membranes. The term Equine Amnionitis and Fetal Loss (EAFL) was developed to describe the condition. This form of abortion had not been previously recognised in Australia. The pathology alone is not specific for EAFL and diagnosis requires demonstration of a combination of certain pathological and bacteriological features. The purpose of this paper is to describe patterns considered consistent with EAFL cases as a working case definition for use by veterinarians and veterinary pathologists in identifying future cases of EAFL. More detailed papers are in preparation to fully describe the epidemiological, histopathological, and microbiological aspects of EAFL.     

Meniscal Mineralization in Domestic Cats

Objective: To (1) determine prevalence of radiographically detectable meniscal mineralization in domestic cats and (2) to evaluate the association between meniscal mineralization and degenerative joint disease (DJD). Study Design: Prospective study. Animals: Client‐owned cats (n=100) and 30 feline cadavers. Methods: Randomly selected client‐owned cats were used to determine the prevalence of meniscal mineralization. Stifles from feline cadavers were used to evaluate the relationship between meniscal mineralization (using high‐resolution X‐ray), radiographic DJD, and cartilage damage. Menisci were evaluated histologically. Results: Forty‐six percent of the client‐owned cats had meniscal mineralization detected in 1 or both stifles. Pain scores were not significantly different between stifles with meniscal mineralization and those with no radiographic pathology (P=.38). Thirty‐four of 57 cadaver stifles had meniscal mineralization, which was always located in the cranial horn of the medial meniscus. Percentage mineralization of the menisci was significantly correlated with the cartilage damage score of the medial femoral (r²=0.6; P<.0001) and tibial (r²=0.5; P<.0001) condyles as well as with the total joint cartilage damage (r²=0.36; P<.0001) score and DJD score (r²=0.8; P<.0001). Conclusion: Meniscal mineralization is a common condition in domestic cats and seems to indicate medial compartment DJD. Clinical Relevance: Clinical significance of meniscal mineralization is uncertain. Further work is needed to determine if the meniscal mineralization is a cause, or a consequence of joint degeneration.     

Meniscal translocation and deformation throughout the range of motion of the equine stifle joint: an in vitro cadaveric study

Reason for performing study: By study of the translocation and deformation of equine menisci throughout the range of motion, it may be possible to identify potential mechanical factors in the pathogenesis of injury to the cranial horn of the medial meniscus. Objective: To quantitatively document meniscal translocation and deformation using radiographic and MR imaging, and to evaluate for potential variation between the medial and lateral menisci. Methods: Radiographic markers were embedded in the periphery of the menisci in 6 cadaver stifles. Proximal‐distal radiographs were taken at 15° intervals ranging from full flexion (30°) to full extension (160°). Magnetic resonance imaging sequences of 3 additional cadaver stifles were obtained in axial and sagittal planes at the predetermined stifle angles. Results: A significantly greater overall mean cranial‐caudal translocation (1.6 times) of the lateral meniscus relative to the medial was seen from full extension to full flexion (P = 0.002). The cranial horn of the medial meniscus was the least mobile of the 4 horns, yet a significant cranial displacement relative to the cranial horn of the lateral meniscus was seen in the terminal 10° of extension. MRI images revealed a significantly greater axial compressive strain in the cranial horn of the medial meniscus relative to the cranial horn of the lateral meniscus in the terminal 10° of extension (P = 0.017). Conclusion: The equine menisci exhibit a cranial‐caudal translocation over the tibia throughout the range of motion. While the cranial horn of the medial meniscus is the least mobile of the 4 horns, it undergoes significant cranial translocation and axial compression in the terminal 10° of extension. Potential relevance: Hyperextension of the stifle may place the cranial horn of the medial meniscus at risk of injury and thus explain the higher prevalence of meniscal tears at this location.     

Long-term successful outcome of a Streptococcus equi subspecies equi brain abscess

We previously described successful treatment, including surgical drainage, of a Streptococcus equi subspecies equi brain abscess that caused severe neurological deficits in a 7-year-old Quarter Horse mare. This report details the long-term successful outcome of the case, findings of a magnetic resonance imaging (MRI) study performed 14 years after surgery and necropsy findings 18 years after initial treatment. Despite persistent cerebral and midbrain lesions detected by MRI and at necropsy, the mare returned to serviceable function within a year of initial treatment and had a successful performance career for over 10 years until carpal arthritis prompted retirement. This case demonstrates that brain abscess in horses can be successfully managed by combined medical and surgical treatment.     

Effects of organic manure and chemical fertilizer on soil fertility and productivity of plant and ratoon crops of sugarcane

A long-term field experiment was initiated in November, 1967 at Research Area of Department of Soil Science to study the response of nitrogen to pearl millet-wheat cropping system at various doses and modes of farmyard manure application. The soil organic carbon increased with farmyard manure application and ranged from 0.68% in control to 1.82% in the plot receiving the highest annual dose (90 Mg ha^?1) of farmyard manure. To study the contribution of farmyard manure on the productivity of pearl millet and wheat crops, the constants (intercept and slope) were determined between the grain yield of pearl millet and wheat crops with increasing dose of fertilizer nitrogen. Another linear regression was fitted between the intercept of the linear model and the soil organic carbon content. It has been observed that with each unit increase in the soil organic carbon, the productivity of pearl millet increased by 273 kg ha^?1 and that of wheat by 1591 kg ha^?1. The regression between the slope and soil organic carbon was linear in case of pearl millet (R² 0.49) but in case of wheat there was no relationship.