TSE pathogenesis in cattle and sheep

Many studies have been undertaken in rodents to study the pathogenesis of transmissible spongiform encephalopathies (TSE). Only a few studies have focused on the pathogenesis of bovine spongiform encephalopathy (BSE) and scrapie in their natural hosts. In this review, we summarize the most recent insights into the pathogenesis of BSE and scrapie starting from the initial uptake of TSE agents and crossing of the gut epithelium. Following replication in the gut-associated lymphoid tissues (GALT), TSE agents spread to the enteric nervous system (ENS) of the gut. Infection is then carried through the efferent fibers of the post-ganglionic neurons of the parasympathetic and sympathetic nervous system to the pre-ganglionic neurons in the medulla oblongata of the brain and the thoracic segments of the spinal cord. The differences between the pathogenesis of BSE in cattle and scrapie in sheep are discussed as well as the possible existence of additional pathogenetic routes.     

Application of polymerase chain reaction-denaturing gradient gel electrophoresis for comparison of direct and indirect extraction methods of soil DNA used for microbial community fingerprinting

 We used polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) to compare bacterial community patterns obtained with target DNA extracted from a soil by direct and indirect methods. For this purpose, two direct extraction methods, i.e. cell lysis by bead beating and cell disruption by grinding in liquid N, and two indirect methods, i.e. cell extraction followed by DNA extraction, and combined RNA/DNA extraction from the bacterial cell fraction, were performed. Crude extracts were purified and amplified using universal bacterial primers. PCR products were then analysed by DGGE, and similarity between the profiles obtained was determined by unweighted pair group with mathematical averages clustering. The results showed clear profiles that presumably represented the dominant bacterial fractions in the samples. The profiles generated by all four methods were similar, indicating that the methods were of approximately equal efficiency in the extraction of target DNA representative of the soil bacterial community. However, the patterns of clustering also indicated that different populations of bacteria could be detected in the same soil using different soil DNA extraction methods. The application of two dilution levels of DNA in PCR-DGGE showed that the most stable profile of the soil bacterial community could be generated by the direct methods. The indirect methods gave clustered profiles at both dilution levels. It is likely that these methods extracted DNA from a major, easily desorbed, bacterial fraction, consisting of low-density populations. PCR-DGGE was found to be a suitable technique with which to assess differences in methods for DNA extraction from soil, which can be further used for the determination of microbial community diversity at the molecular level. Received: 22 June 1999     

Plasma renin activity and plasma concentrations of aldosterone, cortisol, adrenocorticotropic hormone, and alpha-melanocyte-stimulating hormone in healthy cats

A pathogenetic role of the renin-angiotensin-aldosterone system has been implicated in cats in both systemic arterial hypertension and hypokalemic myopathy. Yet, measurement of plasma aldosterone concentrations (PACs) and plasma renin activity (PRA) has not unequivocally pointed to hyperaldosteronism as a cause of these conditions. To obtain appropriate reference ranges, this study included a large number (130) of healthy house cats of different breeds without a history of recent illness and plasma concentrations of urea and creatinine below the upper limit of the respective reference ranges. In addition, the pituitary-adrenocortical axis was studied by measuring plasma concentrations of adrenocorticotropic hormone (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), and cortisol. Reference ranges for PACs (110-540 pmol/L; 40-195 pg/mL), PRA (60-630 fmol/L/s; 0.3-3 ng/mL/h), and the aldosterone to renin ratio (ARR) (0.3-3.8) were very similar to those established in the same laboratory for humans in a supine position. No breed differences were found. The ARRs in neutered cats were significantly higher than in intact cats, primarily because of low PRA in neutered cats. The ARRs of cats > or = 5 years of age were significantly higher than those of cats < 5 years of age. The plasma concentrations of ACTH, alpha-MSH, and cortisol did not correlate significantly with PAC. Thus, although blood sampling was performed in cats in nonstandardized positions and was associated with a wide variation of stress responses, the references ranges of PAC, PRA, and ARR were similar to the relatively narrow limits established for humans under standardized conditions. The effects of neutering and aging on PRA and ARR warrant further investigation.     

Haemonchus spp. in sheep farmed under resource-poor conditions in South Africa--effect on haematocrit,conjunctival mucous membrane colour and body condition

A longitudinal study was conducted on the differential faecal egg counts, haematocrits and body condition scores of sheep belonging to resource-poor farmers at Rust de Winter, Gauteng province, and Kraaipan, North West Province, South Africa. The animals were scored for level of anaemia using the FAMACHA method, an assay for the clinical evaluation of anaemia caused by Haemonchus spp. Periods of higher Haemonchus egg counts occurred from October to March for sheep at Rust de Winter and from September/October to February or April for sheep at Kraaipan. Lower haematocrit values were registered during these periods as was a higher incidence of anaemic conjunctival mucous membrane colour scores compared to the period April to September. No clear relationship between the faecal egg counts and the body condition scores was evident. Although wider application of the FAMACHA system in sheep raised by resource-poor farmers should be investigated, the present study indicates that this method may certainly prove to be a valuable worm control strategy for such livestock owners.     

Development of an attenuated apathogenic reovirus vaccine against viral arthritis/tenosynovitis

A fully attenuated apathogenic reovirus vaccine was developed by 235 serial passages of S1133 strain avian reovirus in embryonating chicken eggs and 100 additional passages in chicken embryo fibroblast (CEF) cultures, 65 of which were cultured at 32 C. Chickens with and without maternal antibodies to avian reovirus were vaccinated subcutaneously at 1 day of age and challenged via footpad at 14 days of age. It appeared that the 40th, 66th, and 100th CEF passage levels were apathogenic at doses ranging from 10(2.5) to 10(6.8) TCID50/chick. No gross or microscopic lesions of tenosynovitis developed in vaccinated chicks. Vaccinated chicks were protected against challenge; unvaccinated control chickens were not.     

Preliminary Studies on the Concentration of Na+,K+-ATPase in Skeletal Muscle of Draught Cattle in Mozambique: Effect of Sex,Age and Training

The effect of training on the potential for work in draught cattle was assessed by measuring the Na⁺,K⁺-ATPase in the muscle cell membrane and the elevation in the concentration of K⁺ in plasma during exercise. Biopsies of the semitendinosus muscle and venous blood samples were taken from the cattle used for draught work in Mozambique. No differences were found in the plasma ion or Na⁺,K⁺-ATPase concentrations in samples taken from Nguni, Africander and Angoni breeds. There were no significant differences in plasma ions (Na⁺, K⁺ and Cl^–) or muscle Na⁺,K⁺-ATPase concentrations between the Angoni males and females, although the males showed an increase in Na⁺,K⁺-ATPase with age, while the females showed a decrease. The increase in males might be attributed to their higher level of activity in the herds than that of females. After a training period of 15 days, a significant increase in Na⁺,K⁺-ATPase concentration in semitendinosus muscle was found in Angoni cattle. In females, this was significant after 8 days of training (about 30%); in males after 15 days of training (about 16%). On day 15, there was a reduction in the elevation of plasma K⁺ during the 2 h of draught work, indicating an increased capacity of the Na⁺,K⁺ pumps to maintain the extracellular K⁺ concentration in working muscles and a possible delay in the moment of fatigue.     

Combined transscleral diode laser cyclophotocoagulation and Ahmed gonioimplantation in dogs with primary glaucoma: 51 cases (1996-2004)

OBJECTIVE: To evaluate the combined diode laser cycloablation procedure and adjunctive Ahmed gonioimplant use in dogs with primary glaucoma. DESIGN: Retrospective study. ANIMALS: 48 dogs, 51 eyes with primary glaucoma. PROCEDURE: Medical records from two large private clinical ophthalmology services were reviewed. Signalment, duration of glaucoma, gonioscopic evaluation, laser power and duration settings, immediate postoperative and final intraocular pressure and visual results, short and long-term visual outcome, and surgical complications were recorded. RESULTS: The age range of affected dogs was 3.0-14.0 years, with a mean age of 7.5 +/- 2.6 years. Eleven pure breeds were represented, with the most common being the American Cocker Spaniel. The sex distribution was 22 neutered males, 1 intact male, 23 spayed females, and 2 intact female dogs. The right eye was affected in 33 cases, and the left eye in 18 cases. The average total joules, which was administered with the diode laser, was 109.6 +/- 23.6 J. Immediate surgical complications included fibrin formation in the anterior chamber (15), corneal ulcers (4), hyphema (7), and focal retinal detachment (1). Long-term complications included cataract formation (8 total, 2 of which were significant, vision-threatening), elevated intraocular pressure (IOP) (6), unstable gonioimplant (1), and glaucoma recurrence (14). Additional surgeries performed on the eyes over the course of study included: intrascleral prosthesis (4), enucleation (1), resection of fibrotic scar tissue (5), and repeat laser cycloablation (8). The dogs were examined for a mean follow-up time of 17.6 months (range: 2-83 months postoperatively). Twenty-nine cases were followed greater than one year. Vision was maintained in 42/51 eyes (82%) in the immediate short-term of this study. In all cases included in the study, good control of IOP was achieved in 39/51 (76%) of eyes, and IOP was poor or uncontrolled in 12/51 (24%) of eyes. Twenty out of 41 eyes (49%) maintained fair to excellent vision six months after surgery. Twelve months postoperative observations demonstrated that 12/29 (41%) of the eyes were still visual. CONCLUSIONS: In primary glaucoma, the combined procedure of laser diode cyclophotocoagulation and Ahmed valve implant was associated with return or maintenance of vision in 42/51 eyes (82%) in the immediate short-term of this study, and a long-term IOP control in 39/51 (76%) of the cases, with 12/29 eyes (41%) visual after 12 months.     

Effect of the route of administration on the mucosal and systemic immune responses to Lawsonia intracellularis vaccine in pigs

In an on‐farm study, 40 weaned piglets aged 3 weeks were vaccinated with Lawsonia intracellularis vaccine orally, IM or IP while a fourth group remained unvaccinated. All vaccinated animals showed increased serum levels of L. intracellularis‐specific IgG antibodies, but significantly elevated concentrations of specific IgG, IgA and cytokines were generated in ileal mucosal secretions from the orally and IP vaccinated pigs when examined at 17 days after vaccination.     

Conduciveness of different soilless growing media to <Emphasis Type="Italic">Pythium</Emphasis> root and crown rot of cucumber under near-commercial conditions

Substrates made from rockwool, coir dust, pumice and perlite were compared for conduciveness to Pythium root and crown rot in cucumber under near-commercial conditions. Rockwool slabs of 7 cm height were more conducive to the Pythium disease than coir dust slabs, pumice or perlite under these conditions. Temperature, oxygen concentration and water content were determined in the substrates to explain differences in conduciveness between the inorganic substrates rockwool, pumice and perlite by differences in the physical conditions. Temperature and oxygen concentration could not explain the differences but the higher disease level on rockwool was associated with a much higher water content of this substrate as compared to coir dust, pumice and perlite. Increasing the height of the substrate from 7 to 14 cm greatly decreased the percentage of diseased plants due to the Pythium disease on rockwool but had no effect on the level of disease on perlite when the substrate had been infested 4 cm below the planting hole. This difference in response in substrate height between rockwool and perlite could be explained by a much larger decrease in water content with substrate height in the rockwool than in the perlite substrate. Temperature in the substrates were above 30 °C for more than 6 h on sunny days in June and reached maximum values of 35 °C or more. These temperatures are highly favourable for the pathogen P. aphanidermatum but will have adverse effects on most biocontrol strains.     

Pathogenesis of reproductive failure induced by Trypanosoma vivax in experimentally infected pregnant ewes

The present study was aimed at investigating the effect of experimental infection by Trypanosoma vivax in different stages of pregnancy, determining the pathogenesis of reproductive failure, and confirming transplacental transmission. We used 12 pregnant ewes distributed into four experimental groups: G1, was formed by three ewes infected with T. vivax in the first third of pregnancy (30 days); G2 comprised three infected ewes in the final third of pregnancy (100 days); G3 and G4 were composed of three non-infected ewes with the same gestational period, respectively. Each ewe of G1 and G2 was inoculated with 1.25 × 10⁵ tripomastigotes. Clinical examination, determination of parasitemia, serum biochemistry (albumin, total protein, glucose, cholesterol, and urea), packed cell volume (PCV), serum progesterone, and pathological examination were performed. Placenta, amniotic fluid, blood and tissues from the fetuses and stillbirths were submitted to PCR. Two ewes of G1 (Ewe 1 and 3) presented severe infection and died in the 34^th and 35^th days post-infection (dpi), respectively; but both fetuses were recovered during necropsy. In G2, Ewe 5 aborted two fetuses on the 130^th day (30 dpi) of pregnancy; and Ewe 6 aborted one fetus in the 140^th day (40 dpi) of gestation. Ewes 2 and 4 delivered two weak lambs that died five days after birth. Factors possibly involved with the reproductive failure included high parasitemia, fever, low PCV, body score, serum glucose, total protein, cholesterol, and progesterone. Hepatitis, pericarditis, and encephalitis were observed in the aborted fetuses. The presence of T. vivax DNA in the placenta, amniotic fluid, blood, and tissues from the fetuses confirms the transplacental transmission of the parasite. Histological lesion in the fetuses and placenta also suggest the involvement of the parasite in the etiopathogenesis of reproductive failure in ewes.