Study of cattle persistently infected with bovine viral diarrhea virus that lack detectable virus in serum

OBJECTIVE: To determine whether cattle persistently infected with bovine viral diarrhea virus (BVDV) that lack virus detectable in serum by use of the immunoperoxidase microtiter assay (IPMA) can transmit the virus to susceptible herdmates and determine prevalence of these cattle. DESIGN: Clinical trial and serologic survey. SAMPLE POPULATION: 2 cattle and 1,952 blood samples. PROCEDURE: A persistently infected cow in which virus could not be detected in serum was housed with a BVDV-seronegative steer. Blood and nasal swab specimens were tested via virus isolation and serum virus neutralization. Parallel WBC preparations and sera from blood samples of 1,952 adult cows were screened for BVDV by use of IPMA. RESULTS: The steer seroconverted to BVDV within 4 weeks of contact with the cow. Virus was detected in sera and WBC of 5 adult cows that were verified as persistently infected by retest 3 weeks later. Cattle persistently infected with BVDV in which virus could not be detected in both serum and WBC by use of IPMA were not found. CONCLUSION AND CLINICAL RELEVANCE: Cattle persistently infected with BVDV in which virus cannot be detected in serum by use of IPMA may serve as virus reservoirs for infecting susceptible cattle. Persistent infection was detected at a prevalence of 0.26%. Screening adult cattle by use of IPMA on serum samples appears to be a reliable means of detecting persistent infection with BVDV. Prevalence of cattle persistently infected with BVDV that have negative results of IPMA on serum is extremely low.     

Effects of growth hormone on female reproductive organs

During the last decade many experiments have been performed to study the effects of growth hormone (GH, somatotropin) on reproductive functions. Most of the studies found only slight or no effects of GH treatment, both on the oestrous cycle and on gonadotropin, progesterone. or oestrogen serum levels. In GH-treated animals, elevated levels of insulin-like growth factor I and GH in the serum could be correlated with an increased number of small (< 5 mm in diameter) ovarian follicles, possibly as a consequence of a reduction of apoptosis and follicular atresia. There is still controversy over the effects of GH on in vivo and in vitro embryo production and on the gestation period. Recent studies produced some evidence that GH-receptor is expressed in ovarian tissue, implying a direct role for GH in the ovary.     

Life cycle of Frenkelia. IV. Pathomorphological findings in the organs of experimentally infected bank voles]

In 1975 the buzzard (Buteo buteo) was found to be the final host of Frenkelia clethrionomyobuteonis. After this discovery it became possible to investigate systematically the pathomorphology of the infection in the intermediate host, the bank vole (Clethrionomys glareolus). Fifty bank voles were infected orally with a suspension of sporocysts recovered from the faeces of experimentally infected buzzards. Each rodent receive 7000 sporocysts. Six controls each were given a faecal suspension from a non-infected buzzard. The voles were killed between 1 and 140 days after infection and examined histologically. Between the 5th and 8th day of the infection during the schizogonic multiplication of the parasite a focal necrosis of liver cells and of the liver parenchyma is observed followed by a reversible resorptive inflammation associated with siderophagia and the occurrence of giant cells. The spleen was spodogenously enlarged up to twice its normal size. There also was haemosiderosis of the bone marrow, the liver and the spleen up to 25 days after infection. At the same time the erythropoiesis in the bone morrow, the spleen and in the lymph nodes increased; there also was a lymphoid hyperplasia in spleen and lymph nodes. About 10 days after infection a reversible infiltration with lymphocytes and plasma cells developed in the liver, heart and brain. This infiltration was again detectable as perivascular and meningeal reactions in the brain after the 49th day after infection. The second asexual multiplication of the parasite was seen histologically in the grey and white matter of the central nervous system after the 18th day of infection. The developing cysts increased in size continuously thereby compressing the surrounding nervous tissue. Disseminated focal necrosis with resorptive inflammatory components was prominent in the parenchyma of the brain after the 49th day of infection. It was possible to differentiate between damage in single organs and systemic pathological lesions. The lesions in single organs were directly connected with the development of parasitic stages in the liver (schizonts) and in the brain (cysts). The generalized lesions occurred in the haemopoietic system after an impairment of the blood during the first asexual multiplication. They also occurred in the immunocytic systems after the first and during the second asexual multiplication and during the relatively late cystic phase of the parasite in the brain. The pathogenesis of the disintegration of blood cells is not clear. The immunocytic reaction can be considered an immunological response of the host against the parasite. The effect of the development of the cysts on the function and structure of the central nervous system is expected to lead to an increasing impairment of the motility of the intermediate host.     

Genetic and environmental parameters for steer ultrasound and carcass traits

Carcass measurements for weight, longissimus muscle area, 12-13th-rib fat thickness, and marbling score, as well as for live animal measurements of weight at the time of ultrasound, ultrasound longissimus muscle area, ultrasound 12-13th-rib fat thickness, and ultrasound-predicted percentage ether extract were taken on 2,855 Angus steers. The average ages for steers at the time of ultrasound and at slaughter were 391 and 443 d, respectively. Genetic and environmental parameters were estimated for all eight traits in a multivariate animal model. In addition to a random animal effect, the model included a fixed effect for contemporary group and a covariate for measurement age. Heritabilities for carcass weight, carcass longissimus muscle area, carcass fat thickness, carcass marbling score, ultrasound weight, ultrasound longissimus muscle area, ultrasound fat thickness, and ultrasound-predicted percentage ether extract were 0.48, 0.45, 0.35, 0.42, 0.55, 0.29, 0.39, and 0.51, respectively. Genetic correlations between carcass and ultrasound longissimus muscle area, carcass and ultrasound fat thickness, carcass marbling score and ultrasound-predicted percentage ether extract, and carcass and ultrasound weight were 0.69, 0.82, 0.90, and 0.96, respectively. Additional estimates were derived from a six-trait multivariate animal model, which included all traits except those pertaining to weight. This model included a random animal effect, a fixed effect for contemporary group, as well as covariates for both measurement age and weight. Heritabilities for carcass longissimus muscle area, carcass fat thickness, carcass marbling score, ultrasound longissimus muscle area, ultrasound fat thickness, and ultrasound-predicted percentage ether extract were 0.36, 0.39, 0.40, 0.17, 0.38, and 0.49, respectively. Genetic correlations between carcass and ultrasound longissimus muscle area, carcass and ultrasound fat thickness, and carcass marbling and ultrasound-predicted percentage ether extract were 0.58, 0.86, and 0.94, respectively. The high, positive genetic correlations between carcass and the corresponding real-time ultrasound traits indicate that real-time ultrasound imaging is an alternative to carcass data collection in carcass progeny testing programs.     

Towards the first linkage map of the<Emphasis Type="Italic">Didymella rabiei</Emphasis> genome

A genetic map was developed for the ascomyceteDidymella rabiei (Kovachevski) v. Arx (anamorph:Ascochyta rabiei Pass. Labr.), the causal agent of Ascochyta blight in chickpea (Cicer arietinum L.). The map was generated with 77 F₁ progeny derived from crossing an isolate from the U.S.A. and an isolate from Syria. A total of 232 DAF (DNA Amplification Fingerprinting) primers and 37 STMS (Sequence-Tagged Microsatellite Site) primer pairs were tested for polymorphism between the parental isolates; 50 markers were mapped, 36 DAFs and 14 STMSs. These markers cover 261.4cM in ten linkage groups. Nineteen markers remained unlinked. Significant deviation from the expected 1:1 segregation ratios was observed for only two markers (Prob. of χ²<0.05). The implications of our results on ploidy level of the asexual spores are discussed. http://www.phytoparasitica.org posting Sept. 5, 2002.     

Stimulating effects of the insecticide chlorpyrifos on host searching and infestation efficacy of a parasitoid wasp

Hymenopterous parasitoids play an important role in the control of insect populations. During oviposition, Hymenopterous parasitoids use cues such as odours from their environment to locate their specific host. Leptopilina heterotoma (parasitoid of Drosophila larvae) locate their host by probing the substrate with the ovipositor. This behaviour can be induced by the odour of the host substrate alone. We analysed the sub-lethal effects of chlorpyrifos at LD20 on the probing activity in response to a fruit odour (banana). The insecticide increased the percentage of females spontaneously probing in response to the odour. Parasitoid females were then conditioned to associate banana odour with the oviposition in host larvae. This conditioning enables parasitoids to memorize the odour and to increase their probing response to this odour. During the olfactory conditioning, females exposed to the insecticide found and oviposited in host larvae more quickly than control females. One hour after the olfactory conditioning, females exposed to the insecticide presented a higher increase of their probing response to the odour than controls. Twenty-four hours after conditioning, the stimulation produced by chlorpyrifos was no longer perceptible, but the level of response of conditioned females was still higher than that of non-conditioned females, showing that odour memory was not impaired by the insecticide treatment. These sub-lethal effects, that stimulate host searching by parasitoids without impairing odour memorization, could increase their parasitic efficiency.     

Land-cover and structural changes in a western Norwegian cultural landscape since 1865, based on an old cadastral map and a field survey

Many studies of land-cover and structural changes in cultural landscapes have used historical maps as a source for information about past land-cover. All transformations of historical maps onto modern coordinate systems are however burdened with difficulties when it comes to accuracy. We show that a detailed land survey of the present landscape may enable transformation of an old cadastral map directly onto the present terrain with very high accuracy. The detailed resulting map enabled us to locate remnants of semi-natural grasslands and man-made structures with continuity from 1865 and to test hypotheses about relationships between landscape changes and landscape characteristics. The main land-cover change 1865–2002 was decrease of arable fields, and addition of three new land-cover classes: horticultural, orchard and abandoned areas. Of the 330 man-made structures present in 1865, only 58 remained in 2002, while 63 new structures had been built after 1865. We found that semi-natural grasslands with continuity since 1865 were situated on ground with significantly lower production capacity than mean 1865 production capacity. The man-made structures with continuity since 1865 were also associated with areas with significantly lower production capacity than the 1865 mean, situated in significantly steeper terrain but not further from the hamlet. Our study illustrates the potential of digitised and accurately transformed historical cadastral maps combined with detailed field surveys for analysis of land-cover and structural changes in the cultural landscape.