Detection of calves persistently infected with bovine pestivirus in a sample of dairy calves in south-eastern Queensland

Objective To determine the proportion and incidence of calves persistently infected with bovine pestivirus in calves (n = 1521) supplied to the Tick Fever Research Centre and to assess the test regime to detect calves persistently infected with bovine pestivirus.
Design Calves, 1 to 6 weeks old, selected for use in the production of the tick fever vaccine were collected from 21 properties in 56 separate groups between October 1990 and December 1996. Each group was examined for the presence of calves persistently infected with bovine pestivirus.
Procedure All calves were routinely tested for antibody to bovine pestivirus and bovine pestivirus antigen using a serum neutralisation test and an antigen-capture ELISA, respectively. Pooled lymphocyte samples from calves were also monitored for bovine pestivirus by inoculation of sheep. Whole herd testing was carried out in eight herds, using a serum neutralisation test as a screen test followed by an antigen-capture ELISA of cattle with a serum neutralisation test titre of less than 32.
Results Fourteen of the 1521 calves tested (0.9%), were detected as persistently infected and the incidence ranged from 0.0 to 3.0 % per year over 6 years. Persistently infected calves were found in 13 of the 59 groups and originated from 7 of the 21 herds used. In whole herd testing on the properties of origin, cattle persistently infected with bovine pestivirus were detected in four of the eight herds tested
Conclusions The proportion of calves persistently infected with bovine pestivirus is similar to that in other countries and indicates that bovine pestivirus could be a significant cause of economic loss in Australian cattle herds. In detecting calves persistently infected with bovine pestivirus, the combination of sheep inoculation, paired antigen-capture ELISA and serum neutralisation tests appeared to be highly sensitive and specific.     

Feline attractant, cis,trans-nepetalactone: metabolism in the domestic cat

cis,trans-Nepetalactone, the biologically active component of catnip, was force-fed to the domestic cat. When the (14)C-labeled compound was fed, 86 to 94 percent of the radioactivity was recovered in the urine, 1 to 2 percent was found in the feces, and 1 to 12 percent was collected as carbon dioxide. The major (50 to 75 percent) metabolite was alpha-nepetalinic acid, which was excreted in the urine together with small amounts of dihydronepetalactone, unchanged cis,-trans-nepetalactone, and several unidentified compounds. No marked physiological or histological eflects were observed when 20 to 80 milligrams of cis, trans-nepetalactone was administered orally. This is the first report on the metabolism of a mammalian attractant.     

Chronic effects of reduced dissolved oxygen on Daphnia magna

Daphnia magna, initially exposed when less than 48 h old, were maintained at reduced dissolved oxygen (DO) concentrations for 26 days. Exposure was accomplished in a continuous flow recirculating water system. Number of days to first brood, number of young in the first brood, total number of young produced, and dry weight were parameters measured. Statistical analyses show the Daphnia exposed to the lowest DO concentration tested (1.8 mg l^?1) had significantly reduced responses for all parameters measured. In addition, the organisms exposed to 2.7 mg l^?1 O₂ gained less weight than did the controls.     

Disease of geese caused by a new herpesvirus

A goose flock farmed outdoors in south-eastern Queensland suffered an outbreak of peracute disease with high death rate (97%). Small button ulcers and large plaques overlying lymphocyte aggregates were present on the mucosa of the small intestine of affected birds. Small white foci of necrosis and focal haemorrhages were seen in the livers. Numerous intranuclear inclusion bodies were observed microscopically in hepatocytes and a herpesvirus which grew rapidly in chicken kidney cells was isolated from tissues. Duck virus enteritis (DVE) was suspected but DVE antiserums failed to neutralise the virus. Further serological studies with a limited range of known avian herpesviruses have failed to identify the virus. Experimental transmission resulted in high mortality in geese (100%), lower mortality in ducklings and nil mortality in chickens. Surveillance studies showed no evidence of infection in domestic and wild birds beyond the original farm and the infection appears not to have been established in the area. Wild ducks, which were frequent visitors to the farm dam, were considered the most likely source of the infection.     

A dose-response investigation on the level of resistance to pyrantel citrate in nodular worms of pigs

This study was undertaken to determine the level of resistance against pyrantel citrate in strains of Oesophagostomum quadrispinulatum and Oesophagostomum dentatum which have previously been found resistant to this anthelmintic. Groups of pigs were artificially infected with batches of infective larvae which were previously found either susceptible or resistant to pyrantel citrate. After treatment with 1, 2 and 4 times the recommended dose (14 mg kg-1) of pyrantel citrate, the resistant O. quadrispinulatum population was reduced by 51.0, 76.2 and 86.1%, and O. dentatum by 41.2, 47.9 and 78.5%. The results indicated that O. dentatum was slightly more resistant (P less than 0.05) than O. quadrispinulatum to pyrantel citrate. Treatment of the susceptible worms with 1 and 2 times the recommended dose caused a reduction in worm numbers by 61.0 and 99.4%, respectively.     

Effect of melatonin on induction of estrous cycles in anestrous ewes

To examine the influence of melatonin on seasonality of reproduction, 97 multiparous Suffolk and Suffolk-cross ewes were randomly assigned to one of four treatment (TRT) groups in a 2 X 2 factorial arrangement. Treatments were as follows: 1) control (C); 2) melatonin (M); 3) progestogen (P) implant of norgestomet plus pregnant mare serum gonadotropin (PMSG) injection (P + PMSG) and 4) M plus TRT 3 (M + P + PMSG). From April 3 to June 24 an oral dose of 2 mg M was administered once daily at 1600 to each ewe in TRT groups M and M + P + PMSG. On April 30, ewes in groups P + PMSG and M + P + PMSG were implanted in the ear with 2 mg norgestomet for 13 d. Immediately following implant removal, each ewe was injected with 500 IU PMSG. Blood samples were collected from all ewes twice weekly from March 22 through June 24. Number of estrous cycles per ewe during the TRT period of 82 d (April 3 to June 24) was higher (P less than .05) for M + P + PMSG (2.1 +/- .2) than for C (.3 +/- .2), M (1.5 +/- .2) and P + PMSG (1.1 +/- .2). Control ewes had fewer (P less than .05) estrous cycles per ewe than either M or P + PMSG. Following the induced estrus, 40% of ewes in the M TRT had one estrous cycle; 32% had two or more cycles. For ewes treated with M + P + PMSG, 24% had one cycle, and 32% had two estrous cycles.(ABSTRACT TRUNCATED AT 250 WORDS)