Efficacy of abamectin against natural infections of gastrointestinal nematodes and lungworm of cattle with special emphasis on inhibited, early fourth stage larvae of Ostertagia ostertagi.

The anthelmintic efficacy of abamectin (avermectin B1) was evaluated against gastrointestinal nematodes, including Ostertagia ostertagi inhibited larvae and lungworm, in yearling crossbred beef heifers during late spring. The calves were grazed on contaminated pasture for 10 weeks and then held under conditions free of nematode infection for 3 weeks prior to allotment and treatment on 5 June. Thirteen calves were randomly assigned to two groups of six by restricted randomization on body weights; the extra lightest calf was assigned to the non-treated control group. Group 1 calves were treated with abamectin at 200 micrograms kg-1 body weight by s.c. injection and Group 2 calves were not treated; all were killed at 14 days after treatment. Ostertagia ostertagi was present in all controls; arithmetic mean numbers of adults, developing fourth stage larvae (L4) and inhibited EL4 were 7683, 605 and 36,102, respectively. Other nematode genera present in controls in sufficient numbers for the experiment were Haemonchus placei adults, Trichostrongylus axei adults, Cooperia spp. adults, Oesophagostomum radiatum adults, Bunostomum phlebotomum adults, Dictyocaulus viviparus adults and E5 (immature adults). Abamectin was highly effective (consistently greater than 99% efficacy and P less than 0.05) in removing all nematodes present in treated calves as represented in non-treated controls, including the primary target of Ostertagia ostertagi inhibited EL4. The lowest efficacy was 93.8%, against D. viviparus E5.     

Prevalence of mycoplasmas in the respiratory tracts of pneumonic calves.

The prevalence of mycoplasmas in the respiratory tracts of 148 pneumonic calves originating from 25 herds in the Netherlands is reported. Four types of culture media were used to isolate mycoplasmas: solid modified Edward medium, 2 types of Friis media, and A7B differential agar medium. Mycoplasmas were isolated both from nasal swab specimens and lung lavage fluids collected from live calves and from nasal mucosa and lung tissue specimens collected post mortem. All of the mycoplasma strains isolated could be identified as either Ureaplasma diversum (isolated from 80% of 25 herds), Mycoplasma dispar (92%), M. bovirhinis (88%), M. bovis (20%), M. bovigenitalium (4%), M. arginini (16%), or M. canis (12%). Isolation rates of M. dispar and U. diversum were considerably higher from lung lavage fluids than from nasal swab specimens. M. bovis was detected only in fattening herds and not in dairy herds. The respiratory tracts of 75% of the calves examined contained at least 2 mycoplasma species. In total, 25 different combinations of mycoplasma species were detected in specimens collected from noses and lungs. The pathogenic species U. diversum and M. dispar had not been isolated before in the Netherlands.     

Dinoseb toxicosis in two dogs

Two male English Setters were noticed to be breathing rapidly, hyperexcitable, and atactic after roaming a rural area for 2 hours. Both dogs' cost were stained with yellow liquid. One dog died while en route to the veterinarian. Treatment was begun for the surviving dog for what was initially diagnosed to be organophosphorus or carbamate insecticide toxicosis. Before the diagnosis could be confirmed, the second dog died. The yellow liquid on the dogs' skin was identified as dinoseb in high concentrations. Dinoseb is an acutely toxic, substituted dinitrophenolic herbicide believed to act as an uncoupler of electron transport from oxidative phosphorylation.     

Prevalence of Cryptosporidium sp in equids in Louisiana

In 1985, 22 pony foals reared in a helminth-free environment were tested daily for oocysts of Cryptosporidium sp by use of fecal flotation. Oocysts were found in all foals. Oocysts were first observed in feces collected from foals 9 to 28 days after birth. The mean period of oocyst shedding was 10 days and ranged from 2 to 18 days in individual foals. Diarrhea was observed in 14 of 22 (64%) foals and began before the period of oocyst shedding. Fecal samples also were examined for other infective agents. Salmonella poona was isolated from 1 foal that did not have diarrhea, and coronavirus particles were observed in the feces of 2 foals with diarrhea. Cryptosporidium sp oocysts also were observed in feces of 2 of 17 Thoroughbred foals, 3 of 14 Quarter Horse foals, and 3 of 26 pony foals reared on pastures with their dams. Samples from pasture-reared foals were collected at irregular intervals. Of the 11 Cryptosporidium-positive fecal samples collected from pastured foals, 2 were from foals with diarrhea. A similar survey was conducted during the 1986 foaling season, using the same procedures. Examination of 300 samples from 58 Quarter Horse, Arabian, and pony foals did not detect oocysts. Daily examination of feces from 10 pony foals reared under helminth-free conditions for 30 days also failed to detect Cryptosporidium oocysts.     

Toxic peripheral neuropathy with demyelination in Sprague-Dawley rats given CGS 21595--a 5-lipoxygenase inhibitor.

Male and female Sprague-Dawley rats were given CGS 21595, a pro-drug that is almost immediately metabolized to CGS 19213, a naphthoquinone that acts as a 5-lipoxygenase inhibitor. The compound was administered by gavage to five groups of Sprague-Dawley rats (group Nos. 1, 5, n = 30; group Nos. 2-4, n = 20) at daily doses of 0, 50, 150, 500, or 1,000 mg/kg for 13 weeks. Rats in the higher dose groups had a reduced weight gain, but significant neurologic signs were not observed. A peripheral neuropathy consisting predominantly of myelin destruction in the spinal nerve roots and sciatic nerves in male rats treated with greater than or equal to 150 mg/kg CGS 21595 and in female rats treated with greater than or equal to 50 mg/kg CGS 21595 for 13 weeks. This lesion was not fully reversible after a recovery period of 4 weeks. Lesions consisted of ballooning of myelin sheaths, infiltration by macrophages, demyelination, and occasional areas of remyelination. Axons were generally preserved, and the brain and spinal cord were not affected. Male and female rats in all treatment groups had cytoplasmic hyaline droplets in the proximal renal tubules. This change was reversible after 4 weeks and was not associated with any other adverse effects on the kidney.     

Effects of Added Substrate on Production of Red Swamp Crawfish, Procambarus clarkii, in Earthen Ponds without Planted Forage

The effects of addition of substrate consisting of plastic mesh fencing to experimental earthen ponds were evaluated for the culture of the red swamp crawfish, Procambarus clarkii, without planted forage. Mean daily yield (kg/ha/d), number of crawfish harvested (number/ha/d), and mean individual harvest weight were compared for ponds with and without substrate during a 2‐yr period. The surface area of added substrate was equivalent to 50% of the bottom surface area of the pond. Mean daily yield in the ponds containing substrate, based on a comparison with that of the previous year, increased by 80.2% and was principally attributed to a 66.7% increase in the number of crawfish harvested. Comparative values for the ponds without substrate were ?13.1 and ?11.7%. For the second year, the treatment‐dependent response was consistent. Mean daily yield for the substrate ponds increased by 48.8% compared to 15.0% for the ponds lacking substrate. The primary benefit of the substrate appears to be provision of refuge and three‐dimensional distribution of crawfish in the pond, thereby reducing the incidence of cannibalism and increasing the total number of crawfish harvested per hectare per day. The benefit of the substrate in a commercial production setting must be weighed against its cost and longevity as well as the conditions of the particular management scenario into which it may be incorporated.     

Feeding Frequency Affects Growth, Not Fillet Composition, of Juvenile Sunshine Bass Morone chrysops×M. saxatilis Grown in Cages

Abstract.— In an effort to feed sunshine bass Morone chrysops × M. saxatilis efficiently, promote optimal growth, and reduce labor costs associated with feeding, sunshine bass were grown in cages and fed one of four feeding frequencies: once/d, twice/d, once every other day (I X/EOD), and twice every other day (2X/EOD) for 21 wk. Juvenile sunshine bass were fed a commercial floating diet containing 40% protein and 11.5% lipid. One hundred fish were hand-counted and stocked into each of 12 3.5-m³ cages with three replications per treatment. At the conclusion of the study, percentage weight gain of sunshine bass fed twice/d was significantly (P < 0.05) higher (1,850%) compared to fish fed all other feeding frequencies. Specific growth rate (SGR) of fish fed twice/d was significantly higher (2.1%/d) compared to fish fed all other feeding regimes, while fish fed once/d had a higher SGR (2.0%/d) compared to fish fed I X/EOD (1.6%/d) and 2X/EOD (1.8%/d). Percentage survival was not significantly different (P > 0.05) among all treatments and averaged 70.4%r. Feed conversion ratio (FCR) of fish fed twice/d was significantly higher (2.40) compared to fish fed all other feeding regimes. Percentage fillet weight of fish fed twice/d was significantly higher (27.8%) compared to all other treatments. Percentage moisture, protein, lipid, and ash in fillet were not significantly different among all treatments and averaged 75.7%, 19.4%, 3.5%, and 1.2%n, respectively (wet-weight basis). Based upon data from the present study, it appears that producers growing juvenile sunshine bass in cages may want to feed fish twice daily. This feeding regimen allows for higher growth rates, without adverse effects on body or fillet compositions. However, economic analysis needs to be conducted to determine if feeding twice/d is profitable.     

Histopathological and hematological findings in myeloid leukemia induced by a new feline leukemia virus isolate

Myeloid leukemia was induced by a new feline leukemia virus isolate FeLV-AB/GM-1 in a high proportion of cats. The latency period was short. Three to 5 weeks after infection early changes were detectable in the bone marrow, and cats developed leukemia 5 to 8 weeks after infection. The results of the present histological and cytological studies suggested that there were two stages in the development of leukemia. The first stage appeared to be equivalent to the syndrome of bone marrow dysplasia or preleukemia which, however, converted rapidly to leukemia. Cytopenia(s) were the main hematological findings in all preleukemic and leukemic cats. White blood cell counts were low or normal, but the number of leukemic and abnormal cells increased in the peripheral blood with the progression of the disease. This reliable model system lends itself to further studies to elucidate the pathogenesis of myeloproliferative disorders.     

Survival of Leptosphaeria maculans in soil on residues of Brassica napus in South Australia

The survival of Leptosphaeria maculans , which causes phoma stem canker (blackleg), on oilseed rape residues ( Brassica napus ) in South Australia was investigated. Using a quantitative polymerase chain reaction (PCR) assay for L. maculans DNA, the pathogen was mainly detected in the upper 5 cm of the soil profile, including residues on the soil surface. As the size of organic matter particles in the soil decreased, so did the quantity of L. maculans detected in them. To obtain representative data for a field, at least 30 subsamples needed to be collected over the 0·81 ha area studied. In a survey of 49 commercial fields in South Australia, most L. maculans was detected in fields 1 year after oilseed rape had been grown, with less detected after 2 years and negligible amounts 3 years or more after cropping. The diagnostic DNA-based assay for L. maculans reduced the time and cost of studying L. maculans survival in soil and increased the sensitivity and accuracy of results compared with estimates of propagule number of colony-forming units on a semiselective medium.