农林科学最新文献

This review summarises up-to-date research on the diagnosis of gastrointestinal nematode (GIN) infection in livestock and anthelmintic resistance in GIN. It was commissioned to assist funding bodies to prioritise and guide research and extension efforts to improve the health, welfare and productivity of grazing ruminants in the face of challenge with GIN. A comprehensive review of published articles from journals, books and websites was undertaken, with a focus on peer-reviewed articles published between 2000 and 2024 involving genera of GIN in grazing sheep and cattle with economic importance to New Zealand. Suggestions for articles to include were received from 14 experts in GIN diagnostics. This review is a summary of a longer report submitted to the sponsoring organisation. Clinical signs of GIN infection in grazing ruminants in temperate grazing systems are inadequate as triggers for management interventions including anthelmintic treatment as they are visible only after economically significant pathological changes have occurred. Livestock producers benefit from monitoring GIN burdens using faecal egg counts (FEC) or associated signals such as weight gain. In future, they may use remote monitoring devices for activity in animals, as well as estimating pasture larval contamination. Methods of diagnosing GIN infections using automated FEC devices have improved the convenience of monitoring parasite burdens compared with traditional laboratory methods. However, a lack of quality control measures and a gap in training of skilled technicians for larval differentiation may lead to a shortage of diagnostic capability. Current methods of diagnosing anthelmintic resistance, particularly FEC reduction tests, are not likely to be replaced by laboratory assays in the near future and attention should be focused on facilitating application of new FEC technologies for both animal monitoring and resistance diagnosis. Extension and application of currently available methods and technology will improve animal health and productivity in ruminant grazing systems in the short term. Adoption of novel technologies for remote animal monitoring, practical tools for estimating pasture larval contamination and promoting genetic selection for immunity and resilience to GIN in both sheep and cattle will further enhance productivity in the long term.

Case history: In early summer, a wild fledgling kererū (Hemiphaga novaeseelandiae) was admitted to a wildlife hospital in Dunedin after falling from its nest and being found on the ground.

Clinical findings: The bird was underweight, weighing only 391 g (expected weight > 450 g), and determined to be in poor body condition based on palpation of pectoral muscle mass. There was bilateral periorbital swelling and ocular discharge with caseous material blocking the choana. Samples of the ocular and choanal discharge were collected and submitted for molecular testing. General anaesthesia was required for further radiographic assessment, and the bird was stabilised for 48 hours with oral electrolytes and antimicrobial and analgesic therapy with doxycycline, meloxicam, and tramadol administered orally twice daily via crop tube and voriconazole administered once daily. Chloramphenicol was applied topically to the eyes twice daily. Subsequently, due to the severity of the gross and radiographic lesions, the likelihood of the need for an extended period of treatment, the age of the chick, its weakened and underweight condition and the risk of imprinting, the bird was euthanased while under general anaesthesia.

Laboratory and pathological findings: PCR testing ruled out Chlamydia psittaci as a cause of morbidity and instead identified Mycoplasma columborale. On gross post-mortem examination, there was caseous material in the periorbital tissues, sinuses and choana. Samples of the choanal discharge grew a moderate mixed growth of Escherichia coli and Enterococcus faecalis.

Diagnosis: Severe pyogranulomatous sinusitis associated with infection with M. columborale.

Clinical relevance: This report describes the first isolation of M. columborale in any species in New Zealand and the first diagnosis of mycoplasmosis in a native kererū. The significance of this finding has not yet been determined.

Aims: To describe progress in the reduction of the consumption of antimicrobial drugs by food-producing animals in New Zealand to 2022 and to identify the animal production sectors where progress has been greatest, and those where opportunities remain.

Methods: Data were sourced from official government and industry reports to update previous estimates of consumption (as sales) of antimicrobial products applied to food-producing animals in New Zealand, European countries and the USA. Antimicrobial consumption (AMC) was estimated based on the amount of active ingredient sold, per kg of animal biomass standardised to the probable weight at time of treatment or lifetime mean weight but not slaughter weight (population correction unit; PCU). This methodology is widely used for international comparisons.

Results: The estimated gross consumption of antimicrobials in food-producing animals in New Zealand increased steadily from 2005 to 2013 (from 7.54 to 11.28 mg/PCU). From 2014 to 2018 the estimate flattened to a 5-year rolling mean of 10.40 mg/PCU. In 2019-2021 the consumption dropped. The NZ consumption in 2022 was substantially lower, estimated at 5.84 mg/PCU, 29% less than in 2005 and 45% less than the peak that occurred in 2017.

Conclusions: The use of antimicrobials in food-producing animals in New Zealand is at the lowest rate for nearly 20 years, at 5.8 mg/PCU. Key progress has been made particularly by the poultry industry. Clear future areas to be targeted include prophylactic use of intramammary products applied when drying off dairy cows and a more widespread strategic use in treatment of clinical mastitis.

Clinical relevance: Veterinarians in New Zealand should leverage the significant reduction achieved in AMC by food-producing animals by continuing to improve strategies for antimicrobial use to further reduce the risk of antimicrobial resistance.

Case history: A 9-year-old, spayed, female Golden Retriever presented with an 18-month history of small spots of opacification on the left cornea, a 3-4-month history of a raised spot on the left cornea, and a watery left eye. As a puppy, the dog had sustained an injury to the left cornea. Self-limiting, presumed papillomaviral warts were diagnosed on the face when the dog was 8 months old.

Clinical findings and initial treatment: A full ophthalmic examination revealed a well-circumscribed, pigmented, raised mass immediately adjacent to three smaller pink masses on the left cornea. The corneal tumour was resected by superficial keratectomy. The cornea was treated with topical peginterferon alfa-2a drops post-operatively.

Pathological and molecular findings: The mass was histologically diagnosed as an incompletely excised corneal pigmented squamous cell carcinoma (pSCC) displaying both exophytic growth and superficial stromal invasive characteristics and fine granular brown melanin pigment within the cytoplasm of neoplastic cells. Superficial cells showed evidence of papillomavirus-induced cell changes including enlarged cells with blue-grey cytoplasm and darkly basophilic keratohyalin granules. Canine papillomavirus type 17 (CPV17) DNA sequences were amplified from the carcinoma by PCR using consensus papillomavirus primers.

Diagnosis: Primary corneal pigmented squamous cell carcinoma with concurrent canine papillomavirus type 17 infection.

Outcome: Tumour recurrence was observed 2 years 9 months after surgery. Topical peginterferon alfa-2a drops were recommenced and superficial keratectomy surgery was repeated with concurrent adjunctive strontium 90 plesiotherapy. At the time of writing, the left cornea has healed well with mild fibrosis and vascularisation continuing to reduce.

Clinical relevance: This is the first report of a pSCC of the cornea in any veterinary species. Prominent papillomaviral cytopathology was visible in the corneal pSCC, and PCR confirmed the presence of CPV17.This report expands the differential diagnoses for pigmented corneal masses in dogs. It highlights the importance of obtaining a histopathological diagnosis for pigmented corneal lesions, as the clinical disease course, prognosis and treatment options vary between lesions of different aetiologies. Corneal SCC is locally invasive and can recur without complete excision. Early surgical intervention with clean margins can be curative and restore corneal clarity, vision and patient comfort.

Aims: To determine the genetic makeup of carnivore parvoviruses currently circulating in New Zealand; to investigate their evolutionary patterns; and to compare these viruses with those detected during the previous New Zealand-based survey (2009-2010).

Methods: Faecal samples from dogs (n = 40) with a clinical diagnosis of parvovirus enteritis were voluntarily submitted by veterinarians from throughout New Zealand. In addition, one sample was collected from a cat with comparable clinical presentation. The samples were used for DNA extraction and PCR amplification of viral protein 2 (VP2) of canine parvovirus type 2 (CPV-2). All samples produced amplicons of the expected sizes, which were then sequenced. The viruses were subtyped based on the presence of specific amino acids at defined locations. In addition, VP2 sequences were analysed using phylogeny and molecular network analysis.

Results: The majority (30/40; 75%) of CPV-2-infected dogs were younger than 6 months and 8/40 (20%) were aged between 9 months and 1 year. Most (39/41; 95%) parvoviruses were subtyped as CPV-2c, and one as the original CPV-2. The faecal sample from a cat was positive for feline panleukopenia virus. The majority (37/39; 95%) of New Zealand CPV-2c viruses were monophyletic. The remaining two New Zealand CPV-2c viruses clustered with Chinese and Sri Lankan CPV-2c viruses, separately from the main New Zealand clade.

Conclusions: There has been an apparent replacement of the CPV-2a viruses with CPV-2c viruses in New Zealand between 2011 and 2019. The source of the current CPV-2c viruses remains undetermined. The monophyletic nature of the majority of viruses detected most likely reflects a country-wide spread of the most successful genotype. However, an occasional introduction of CPV-2 from overseas cannot be excluded.

Clinical relevance: Current vaccines appear to be protective against disease caused by the CPV-2c viruses currently circulating in New Zealand. Vaccination and protection from environmental sources of CPV-2 until the development of vaccine-induced immunity remains the cornerstone of protection in young dogs against parvovirus enteritis. Ongoing monitoring of the genetic changes in CPV-2 is important, as it would allow early detection of variants that may be more likely to escape vaccine-induced immunity.

Red and blue lights are the most effective spectral components absorbed by plants and are typically applied in a constant spectrum in plant factory agricultural practices. Research and application of non-constant light modes are relatively rare. In this study, we examined the impacts of varying blue light photon intensity and durations at 5-, 15-, 30-, and 45-min intervals of intermittent exposure on the growth and development of lettuce (Lactuca sativa) in plant factories while maintaining a constant red light photon flux and daily light integral (DLI). Compared to the constant light condition, intermittent blue light irradiation treatments accelerated the emergence of the leafy head trait in lettuce without compromising photosynthetic capacity and biomass. Specifically, intermittent blue light treatment with 15-min intervals led to a reduction of 8 days in the time needed for half of the lettuce plants to reach the heading stage. Furthermore, the petiole bending angle in treated lettuce was just 70.2% of that observed under constant light conditions, with strong correlations between multiple hormone levels and bending angle in petioles. Transcriptome sequencing analyses revealed significant differential expression of signaling-related genes between constant and intermittent blue light treatments. The transient and dynamic expression of light-responsive and hormone metabolism-related genes indicated that 15-min intermittent blue light exposure better maintained the rhythmic differential expression of response genes, leading to different hormone accumulations and consequently accelerating the development of leafy heads.