Natural infection of red deer with bovine tuberculosis

Six bovine tuberculosis-free red deer hinds were introduced in October 1993 to a 1.8 ha enclosure, within a larger field study site known to contain tuberculous possums, and kept there for 9 months. A Mycobacterium bovis-infected possum was found in the vicinity of the deer enclosure 3 weeks after the introduction. Subsequently, a further eleven infected possums were found in the area. The deer were monitored by repeated composite antibody detection ELISA and lymphocyte transformation assays for tuberculosis, interpreted in parallel, by skin testing and by routine culturing of samples collected from potential excretion sites. Lymphocyte transformation assay evidence of M. bovis infection in four hinds was first observed 4 months after introduction. One other hind became bovine tuberculin lymphocyte transformation assay positive in the 5th month. Positive or equivocal bovine reactivity remained evident at most test episodes. A comparative cervical skin test performed in July 1994, shortly before slaughter, was positive in these five hinds. Mycobacterium bovis was recovered off swabs from the oropharyngeal tonsils of two hinds during routine sampling. Detailed necropsy of the six deer revealed a single typical tuberculous lesion in only one, but culturing of various tissue specimens ascertained that the five blood test and comparative cervical skin test-positive animals were all infected. Mycobacterium bovis was cultured from the oropharyngeal tonsils of four and medial retropharyngeal lymph nodes of two of the deer with no typical gross lesions. Six additional tuberculosis-free hinds were introduced to the enclosure in April 1994 and kept there for 12 months. Four of these animals showed a positive lymphocyte transformation assay response to M. bovis after 9 weeks, but no significant reactivity thereafter. Concurrent observational studies suggest that five of the first six deer probably became infected through close inspection and investigation of the tuberculous possums, although the possibility of deer-to-deer transmission cannot be totally excluded. The likely deer-possum contact, and thus exposure to M. bovis, was related to the curiosity and social ranking of the hinds. The second group appear to have had transient exposure to M. bovis, possibly caused by direct contact with the infected hinds introduced earlier. This group never showed any curiosity toward, or interaction with, possums during the periods of observation.     

A real-time polymerase chain reaction assay for the detection of the myxozoan parasite Henneguya ictaluri in channel catfish

Proliferative gill disease (PGD), caused by the myxozoan parasite Henneguya ictaluri, is the most prevalent parasitic infection affecting commercial channel catfish (Ictalurus punctatus) aquaculture. There are currently no effective chemotherapeutic or biological control measures for PGD, which often peaks during the spring and fall when water temperatures are between 16-25 degrees C. The current diagnostic techniques of gross examination of gill clip wet mounts and histopathology are subject to false-negatives during the early stages of infection, and the quantifiable nature of end-point polymerase chain reaction (PCR) is subjective. Consequently, a rapid and more sensitive quantitative real-time PCR assay was developed for the detection of H. ictaluri during the early stages of infection in channel catfish. A 23 base-pair TaqMan probe was designed based on previously published H. ictaluri PCR protocols. The sensitivity of the assay was the equivalent of a single H. ictaluri actinospore, and in a pond challenge study, quantitative real-time PCR proved to be more sensitive than gross examination, microscopic examination of gill clip wet mounts, and histopathologic examination of gill tissue sections. Future applications of this assay will focus on developing methodologies to be used in conjunction with current pond-monitoring protocols to evaluate potential treatments and better manage this significant seasonal disease.     

Detection of channel catfish virus DNA in acutely infected channel catfish, Ictalurus punctatus (Rafinesque), using the polymerase chain reaction

Channel catfish virus (CCV) causes an acute haemorrhagic disease in channel catfish, Ictalurus punctatus (Rafinesque), fry and fingerlings. The present study describes a polymerase chain reaction (PCR)-based assay for detection of CCV DNA in the tissues of acutely infected juvenile catfish. The assay is rapid, sensitive and specifically detects CCV DNA derived from epidemiologically distinct viral isolates. The use of two independent PCR primers sets, each specific for particular CCV genes (open reading frames 8 and 59), provides a means to confirm the results and minimize false-positive results. The method identifies CCV DNA in several tissues of acutely infected fish, including the brain, blood, intestine, kidney and liver. The CCV PCR assay is useful for the diagnosis of acute CCV disease and for studies to investigate the molecular basis of CCV pathogenesis.     

Ascorbate Oxidase,Protein Disulfide Isomerase,Ascorbic Acid,Dehydroascorbic Acid and Protein Levels in Developing Wheat Kernels and Their Relationship to Protein Disulfide Bond Formation

Developing wheat kernels of three New Zealand wheat cultivars at one to nine weeks postanthesis (WPA) were analyzed for kernel weight, salt‐soluble protein, salt‐insoluble protein, ascorbate oxidase (AOX), protein disulfide isomerase (PDI), ascorbic acid (AA), and dehydroascorbic acid (DHA). Kernel weight and salt‐soluble protein increased from one to five or six WPA then declined. The amount of salt‐insoluble protein per kernel rapidly increased from two to five or six WPA, then remained constant. AOX activity increased from one to two or three WPA then declined to almost zero at seven WPA. PDI activity increased from one to three WPA, stayed constant to six WPA, then declined about 25%. DHA increased from one to two or three WPA then declined to zero at seven WPA. AA increased from one to three or five WPA then declined to zero at seven WPA. When DHA, at similar concentrations (≈1 mM) to that found in one to six WPA kernels, was mixed with reduced‐gluten proteins, it was reduced to AA. The results are interpreted as a scheme showing that, during the formation of protein‐disulfide bonds, electrons are transferred from nascent protein thiols, ultimately to oxygen, through a series of electron carriers including PDI, AA‐DHA, and AOX.     

Evidence for selection pressure from resistant potato genotypes but not from fungicide application within a clonal Phytophthora infestans population

Insight into pathogen population dynamics provides a key input for effective disease management of the potato late blight pathogen Phytophthora infestans. Phytophthora infestans populations vary from genetically complex to more simple with a few clonal lineages. The presence or absence of certain strains of P. infestans may impact the efficacy of fungicides or host resistance. Current evidence indicates that genetically, the Irish populations of P. infestans are relatively simple with a few clonal lineages. In this study, P. infestans populations were genetically characterized based on samples collected at the national centre for potato breeding during the period 2012–16. The dominance of clonal lineages within this P. infestans population was confirmed and the potential selection pressure of fungicide treatment (2013–15) and host resistance (2016) on this clonal P. infestans population was then investigated. It was found that fungicide products did not notably affect the genetic structure of sampled populations relative to samples from untreated control plants. In contrast, samples taken from several resistant potato genotypes were found to be more often of the EU_13_A2 lineage than those taken from control King Edward plants or potato genotypes with low resistance ratings. Resistant potato varieties Sarpo Mira and Bionica, containing characterized R genes, were found to strongly select for EU_13_A2 strains.     

Effectiveness of a non-surgical alternative to the Mules operation in sheep

Objective To measure changes to the perineal bare area, local tissue reaction and healing responses of young sheep, following intradermal administration of cetrimide and polyvinylpyrrolidone (PVP), with and without ethanol, to the breech and tail. Method A needle‐less injector was used to deposit formulations containing 40 g/L cetrimide and 30 g/L PVP (group 2) or 20 g/L cetrimide, 30 g/L PVP and 15 g/L ethanol (group 3), within the dermis of the tail and the region surrounding the perineal bare breech area of groups (N = 8) of Merino weaner sheep. The dimensions of the perineal bare area (length, width and diagonal distances left and right) and tail width were recorded before and at intervals after treatment for 60 days. Observations of swelling and bruising and scab formation at the treatment sites were recorded for up to 35 days after treatment. Rectal temperatures were monitored for up to 35 days after treatment and bodyweight for up to 60 days after treatment. An untreated control group (group 1) was included. Results Comparison of day ‐3 and day 35 measurement data showed that both treated groups had significantly (P < 0.05) wider breech bare areas compared to the untreated controls and that group 2 sheep had significantly (P < 0.05) longer breech bare areas compared to group 3 sheep or to the untreated controls, which were not significantly different. At this time scabs were still firmly in place on many treated sheep. At day 35 there was no increase in tail bare area caused by either treatment. By day 60 there was no significant difference between the treated and control groups in either the breech or tail regions indicating that the changes present at day 35, were not permanent. Mean weight gain in the groups throughout the 60‐day interval was unaffected by treatment. Intradermal treatment was associated with a significant elevation in body temperature. This effect lasted for 3 days and was associated with signs of discomfort and depressed appearance in at least some of the treated sheep. Bruising was mild to severe in all treated sheep within two days of treatment but was not evident in any sheep by day 21. Mild to moderate swelling was also associated with treatment but was not uniform across sheep in the groups. The tail of one sheep was severely swollen for several days. Swelling remained obvious in most treated sheep until day 14 but was not present at day 21. Conclusion Under the conditions of this study intradermal injection of cetrimide had no permanent effect on bare area measurements on the breech or the amount of wool‐bearing skin on the tail. It also caused signs of discomfort and pain that raise welfare concerns.     

Cytopathological and histopathological diagnosis of canine splenic disorders

Objectives To determine (1) the common types of canine splenic disorders, and the breeds affected, that are diagnosed by cytopathological and histopathological examination in Sydney, Australia and (2) the accuracy of cytopathological examination compared with histopathological examination for the diagnosis of canine splenic disorders. Design 69 cytopathological and 51 histopathological diagnoses of canine splenic disorders presented to the Veterinary Pathology Diagnostic Services, The University of Sydney during 2006 and 2007 were tabulated and analysed; 17 cases examined both cytopathologically and histopathologically during 2001–07 were also analysed. Results The most common cytopathological diagnoses were benign disorders of growth, vascular disturbances and necrosis (29%), followed by no abnormalities detectable (28%), malignant neoplasms (20%), equivocal diagnoses (20%) and inflammatory disorders (3%). The most common breeds were Kelpie crosses and mixed breeds. The most common histopathological diagnoses were benign disorders of growth, vascular disturbances and necrosis (49%), followed by malignant neoplasms (43%) and inflammatory disorders (8%). The most common breeds were German Shepherd Dogs, Boxers and Maltese Terriers. Cytopathological and histopathological diagnoses were in complete agreement in 59% of cases, partial agreement in 29% and disagreement in 12%. Conclusion Benign disorders of growth, vascular disturbances and necrosis were the most commonly diagnosed canine splenic disorders, both cytopathologically and histopathologically. Kelpie crosses presented most frequently for cytopathological examination. German Shepherd Dogs were the most common breed diagnosed histopathologically with haemangiosarcoma. Although cytopathological and histopathological splenic examinations are complementary for diagnosis, this study has shown a high correlation for complete and partial agreement between the two.