Progress in research on tick‐borne diseases: Theileriosis and heartwater

Summary

The rapid population growth in subsaharan Africa necessitates a great increase in animal production in the more humid zones. Vector‐borne diseases occurring in these zones will assume more importance, but are difficult to control. They include theileriosis and heartwater. Recent developments in research on these diseases are presented. Indigenous animal populations in endemic areas, subjected to natural selection, are far less susceptible than exotic stock.

Heartwater, caused by the rickettsia Cowdria ruminantium, transmitted by Amblyomma ticks, causes high mortality in exotic ruminants. It has received much attention in recent years, partly because the disease has been introduced from Africa into the Caribbean and threatens the American mainland. Since the recent success of in vitro culture, much progress in research has been made, but so far prevention still relies mainly on acaricidal tick control; an infection and treatment method is used on a limited scale. Antigenic diversity is a complication for immunization procedures.

Theileria parva (East Coast fever, Corridor disease and January disease) and T.annulata (Mediterranean or tropical theileriosis) are the most pathogenic of the 6 species of this protozoan genus that infect cattle. Great progress has been made in recent years in knowledge on the immunology, the epidemiology, the taxonomy and the chemotherapy of theileriosis. Intensive acaricidal tick control can now be supplemented by an attenuated schizont vaccine against T.annulata, while immunization against East Coast fever is carried out on a limited scale using virulent sporozoite infection and treatment. Research on recombinant vaccines is promising. Antigenic diversity in T.parva is a serious complication.     

A Survey of the Literature (1995–1999) on the Kinetics of Drugs in Camels (Camelus dromedarius)

Recent publications dealing mainly with the kinetics of antiparasitic and antibacterial agents, NSAIDs, and other drugs in camels are briefly reviewed. The kinetic data for most of these drugs indicated that they have longer absorption and elimination half-lives and slower systemic clearance in the camel compared to other animals. This corroborates earlier reports that suggested that the activities of drug-metabolizing enzymes and the capacity to biotransform and eliminate xenobiotics is lower in camels than in other ruminants. There is a clear need to establish basic kinetic data for the camel in order to avoid extrapolation of drug dosage regimens and withdrawal times from data for other animals, as this may result in irrational use of drugs in camels.     

The effect of tick infestation on the serum concentrations of the cardiac biomarker troponin I, acid–base balance and haematobiochemical profiles in camels (Camelus dromedarius)

The aim of the present study was to evaluate the serum concentration of cardiac troponin I (cTnI) in camels with tick infestation as a marker of potential myocardial injury and its prognostication. The effects of acid–base and electrolyte balance and haematobiochemical profiles were also investigated. Twenty-three camels (Camelus dromedarius) with tick infestation and suffering from anorexia, incoordination of movement, unsteady gait, recumbency, opisthotonus, anaemia and reduced production were examined. Ticks were visible, deeply embedded in the skin over the whole body, especially under the neck and around the udder or testis. Of the camels, 15 recovered after treatment and 8 did not. Blood samples were collected from the diseased camels on the day of admission to our clinic. Blood samples were also collected from 12 healthy camels and were used as controls. The mean serum concentration of cTnI in the camels with tick infestation was 1.7?±?1.6 ng/ml compared to 0.03?±?0.02 ng/ml in the controls. The mean serum concentration of cTnI in those camels that recovered was 0.36?±?0.53 ng/ml compared to 3.0?±?1.1 ng/ml in the camels that did not. Venous blood gas alterations included an increase in partial pressure of carbon dioxide and decreases in partial pressure of oxygen and oxygen saturation. Haematological parameters involved decreases of red blood cells, haemoglobin and haematocrit and increases in the mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration. Biochemical parameters included significant elevations in the serum activity of aspartate aminotransferase, creatine kinase and alkaline phosphates. Other biochemical alterations observed were decreases in total protein and albumin and increases in globulin and glucose concentrations. In conclusion, the data of this study suggest the possibility of using cTnI as a biomarker for cardiac injury in camels with tick infestation and for the prognosis of the outcome in the treated animals. Generally, values above 1.0 ng/ml were considered bad prognostic indicators.     

A note on the shelf‐life and spoilage of commercially‐processed chicken giblets

1. When chicken giblet tissues wrapped individually in polythene were stored at 1 °C, “ off” odours were detected in 11 to 14 d with necks (mean 12.3 d) tending to spoil before gizzards, hearts and livers (means 13.0 to 13.7 d).

2. In all cases, the predominant organisms at spoilage were Pseudo‐monas spp. with lower numbers of Acinetobacter spp.

3. Chlorination of process water at about 50 mg total residual chlorine/1 (including 0.1 to 0.9 mg free chlorine/1) extended the shelf‐life of giblets held at 1 °C by up to 3 d, and prior freezing of these tissues gave an extension of 1 to 2 d but combining the two treatments did not have an additive effect.

4. Immersing giblets for 1 min in a solution containing 100 g potassium sorbate/1 (pH 8.0) doubled the shelf‐life of each type of tissue by retarding growth of the normal spoilage microflora.     

A preliminary report on the occurrence of maedi‐visna in sheep in Morocco

Summary

A small scale serological survey for antibodies to maedi‐visna virus among 15 flocks of sheep in Morocco revealed the infection in one flock. Infection appeared to be related with imported sheep. In addition, two abattoir surveys yielded, 0.1% lungs with gross and histological lesions suggestive of maedi.     

A note on the structure and iron‐binding properties of egg‐shell membranes

1. When a solution of ferric ammonium sulphate was added to shell membranes of the domestic fowl, iron infiltrated the mantle (cortex) surrounding the cores of the individual fibres of the membranes.

2. Contraction of warm eggs in ice‐cold colloidal iron caused flooding of pore canals and contamination of the underlying shell membranes with this element.

3. Appreciable contamination of the inner shell membrane with iron persisted for 25 d in infertile eggs stored at 37.5 °C.     

Seasonal dynamics of ticks (Acari: Ixodidae) on horses in the state of São Paulo, Brazil

Natural tick infestations were assessed every 14 days on horses over a 2-year period. Amblyomma cajennense adult ticks were counted individually, without detachment from the horses. Larvae and nymphs of A. cajennense were collected using a rubber scraper that scratched engorged immature ticks from the host. Adult females of Anocentor nitens larger than 4mm length were counted on the horses. Blood samples were also obtained from the horses every 14 days and macroclimatic data were obtained for the study period. Infestations of A. cajennense demonstrated distinct peaks of activity for each of the three parasitic stages over each 12-month period, showing a 1-year generation pattern. Larvae predominated from April to July and nymphs from June to October. Adults predominated from October to March with a greater number of adult males than females. Although other studies on seasonal dynamics in the states of Rio de Janeiro and Minas Gerais were performed with the free-living stages of A. cajennense on pastures, the present study in the state of S?o Paulo, performed with the parasitic stages of A. cajennense on horses, showed similar results to those observed in other states. Infestations by A. nitens demonstrated distinct peaks of activity of adult females (>4 mm), suggesting different tick generations during the year. Infestation with A. nitens was much higher in the first year than the second year which may have been related to horse nutritional status and stocking rate. Although several climatic variables showed statistical significant correlation (r) with tick counts, the determination coefficients (R(2)) were always lower than 0.40, suggesting that any single significant variable (i.e. mean temperature) would not explain the tick distribution pattern over the year. The highest peaks of A. nitens females (>4 mm) were significantly associated with decrease in horse packed cell volumes (R(2)=0.603). The ears and the perineum, tail and groin region accounted for around 70% of all A. nitens females counted on the horses.     

The Impact of Demographic,Social, and Environmental Factors on the Development of Steroid‐Responsive Meningitis‐Arteritis (SRMA) in the United Kingdom

Background

Steroid‐responsive meningitis‐arteritis (SRMA) is an inflammatory disease of dogs that is suspected to be immune‐mediated. The development of other immune‐mediated diseases has been linked to vaccinations, time of the year, geographic location, sex, neuter status, and breed.

Hypothesis/Objectives

To identify if the development of SRMA is associated with time of year, vaccination, geographic location, sex, neuter status, and breed.

Animals

Sixty SRMA cases and 180 controls, all ≤24 months of age and matched for year of presentation, from a referral hospital population in the United Kingdom.

Methods

Retrospective case‐control study with unconditional logistic regression analysis.

Results

Beagles (P = .001), Border Collies (P = .001), Boxers (P = .032), Jack Russell Terriers (P = .001), Weimaraners (P = .048), and Whippets (P < .001) had significantly greater odds of developing SRMA in this population of dogs. Vaccination, time of year, geographic category, sex, and neuter status did not increase the odds of developing SRMA.

Conclusions and Clinical Importance

Only breed increased the odds of developing SRMA. It would be prudent to investigate the genetics of the identified breeds to help elucidate the etiopathogenesis of SRMA.     

Studies on the toxic effects of crambe meal and two of its constituents, 1‐cyano‐2‐hydroxy‐3‐butene (GHB) and epiprogoitrin,in broiler chick diets

1. Studies were undertaken to determine a safe inclusion rate for crambe (Crambe abyssinica) meal in broiler chick diets, and to determine the mechanism for adverse effects by investigating its constituents; l‐cyano‐2‐hydroxy‐3‐butene (CHB) and 3‐butenyl glucosinolate (epi‐progoitrin, E‐PG).

2. Crambe meals were prepared to differ in E‐PG (19, 36 and 40 g/kg) and CHB contents (0.1, 0.7 and 1.9 g/kg), and with either active or inactive thioglucosidase.

3. Meals were fed to 7‐d‐old broiler chicks at 50 or 100 g/kg of the diet for 12 or 13 d. In separate studies, isolated E‐PG or CHB were mixed into the diet or administered by gavage to 7‐d‐old broiler chicks in amounts equivalent to 50 or 100 g/kg crambe meal diets for 10 and 12 d, respectively.

4. Weight gain decreased (P<0.05) in chicks fed on the high glucosinolate crambe diets or isolated E‐PG. Food consumption decreased (P<0.05) in chicks fed on the diet containing the high E‐PG meal with active enzyme.

5. Mild liver lesions and increased serum aspartate aminotransferase were found in chicks fed on the diet containing the high glucosinolate meal with active enzyme. Other organs, including thyroids, were normal.

6. Commercially‐processed crambe meal appeared safe at an inclusion rate of 50 or 100 g/kg diet, but could not be recommended at this point for long term feeding.     

Influence of temperature and growth stage on the diurnal fluctuation in the non‐structural carbohydrate content of kikuyu (Pennisetum clandestinum Hochst)

The non‐structural carbohydrates of kikuyu (Pennisetum clandestinum Hochst) seem to consist mainly of sucrose. Total non‐structural carbohydrate content increased rapidly during the morning and reached maximum concentration in the afternoon. After sunset, the concentration decreased rapidly, reaching a minimum level by midnight. Low temperatures resulted in a significantly higher non‐structural carbohydrate content in all plant fractions than at warmer growth temperatures. Non‐structural carbohydrate concentrations were higher in stem tissue than in leaf material and the values were higher in 3‐week than in 6‐week regrowth.     

Communal cattle farmer’s knowledge,attitudes and practices on ticks (Acari: Ixodidae), tick control and acaricide resistance

The aim of this study was to reveal communal farmer’s knowledge, attitudes and practice on ticks and tick-borne diseases affecting cattle, tick control methods used and their knowledge on acaricide resistance. A total of 160 structured questionnaires are prepared and randomly administered to cattle farmers in Sinqu and Elundini communities in the Eastern Cape Province, South Africa. Associations between the area, gender, age, employment, source of income, level of education and farming experience were statistically tested using Chi-square test. Gall sickness (63%) was the most prevailing tick-borne disease in cattle during the summer season (61%). About 59% of the farmers had no knowledge of the effect of tick-borne diseases on cattle production, and 78% of respondents reported that ticks are the major challenge to cattle farming. Pour-on (61%) was the most commonly used acaricidal treatment system with every fortnight (40%) treatment frequency during the summer season and (31%) during the winter season. Pyrethroids (73%) were the most used acaricide compounds to control ticks, and about 65% of respondents perceived to have no knowledge of the use of ethnoveterinary medicines used to control ticks. Inefficacy of acaricide (44%) and undipped animals (42%) were regarded as the major contributing factors to the increased tick population and acaricide resistance. About 85% of respondents perceived that they do not practice acaricide rotation and 88% of the respondents had no knowledge of the acaricide resistance. Within the context of this study, ticks and tick-associated diseases are perceived by these farmers as the most important disease problem their cattle face. Thus, knowledge regarding the epidemiology of ticks and tick-borne diseases is key to control strategies, and farmer training should be encouraged to achieve better control of ticks and the diseases they transmit.

     

Hepatitis in dogs. An indexed bibliography of journal articles (1994–2004)

Transmissible spongiform encephalopathies (TSEs) or prion diseases are unique disorders that are not caused by infectious micro-organisms (bacteria or fungi), viruses or parasites, but rather seem to be the result of an infectious protein. TSEs are comprised of fatal neurodegenerative disorders affecting both human and animals. Prion diseases cause sponge-like degeneration of neuronal tissue and include (among others) Creutzfeldt–Jacob disease in humans, bovine spongiform encephalopathy (BSE) in cattle and scrapie in sheep. TSEs are characterized by the formation and accumulation of transmissible (infectious) disease-associated protease-resistant prion protein (PrP^Sc), mainly in tissues of the central nervous system. The exact molecular processes behind the conversion of PrP^C into PrP^Sc are not clearly understood. Correlations between prion protein polymorphisms and disease have been found, however in what way these polymorphisms influence the conversion processes remains an enigma; is stabilization or destabilization of the prion protein the basis for a higher conversion propensity? Apart from the disease-associated polymorphisms of the prion protein, the molecular processes underlying conversion are not understood. There are some notions as to which regions of the prion protein are involved in refolding of PrP^C into PrP^Sc and where the most drastic structural changes take place. Direct interactions between PrP^C molecules and/or PrP^Sc are likely at the basis of conversion, however which specific amino acid domains are involved and to what extent these domains contribute to conversion resistance/sensitivity of the prion protein or the species barrier is still unknown.     

A comparison of the effects of two low‐calcium diets on egg production in the domestic fowl

1. Hens fed on a diet containing 0–05% calcium virtually ceased egg laying (production <4%) whereas those fed on a diet containing 0–5% Ca maintained production at between 20 and 30%.

2. After a return to a normal diet (3% Ca) egg weight, shell weight, ovarian characteristics and oviduct size were of a similar nature in the two groups, though the differences in egg weight, shell weight and shell calcium were significant at the 1 % level.

3. Bone weight and bone ash did not differ significantly between the groups but after a return to normal rations, bone weight and bone ash became higher in the group that had received the 0.05% Ca diet.

4. There were no clinical signs of bone demineralisation during the experiments.     

Effects of 2 training methods on stress-related behaviors of the dog (Canis familiaris) and on the dog–owner relationship

Instrumental learning plays an important role in dog–human interactions. The recent demand for pet dog training has resulted in the development of various training methods. The present exploratory study aims to compare the effects of 2 training methods on both the behavioral welfare of the dog and the dog–owner relationship: the first method is based on positive reinforcement (appearance of an appetitive stimulus), whereas the second method is based on negative reinforcement (disappearance of an aversive stimulus). The study compared behaviors linked to signs of stress and attentive behaviors toward the owner in 2 dog training schools, which used different methods. Walking on-leash activity and obeying the “sit” command were studied. The results show that dogs from the school using a negative reinforcement–based method demonstrated lowered body postures and signals of stress, whereas dogs from the school using a positive reinforcement–based method showed increased attentiveness toward their owner. However, neither method affected avoidance behaviors. This exploratory study reveals the differential effects of the 2 training methods on dogs' behaviors; it suggests that training methods based on positive reinforcement are less stressful and potentially better for their welfare.     

Effects of sex‐linked imperfect albinism in the chicken (s al‐c) on plasma luteinising hormone concentrations and early egg production

1. When measured before and after the onset of darkness, plasma LH concentrations in 40‐day‐old sex‐linked albino pullets (s^al‐c ) were slightly lower than those of nonalbinos (s ⁺ ).

2. This finding prompted an experiment in which plasma LH concentrations were measured between 12 and 33 weeks of age when daylength was increased at 15 or 21 weeks. Egg production of the early and late maturing albino hens was measured.

3. Plasma LH concentrations overall and at 17 weeks were lower for albinos than for nonalbinos. In the early maturing group egg production of albinos was higher than that of nonalbinos.

4. Results suggest that increased egg production of albinos is not the direct result of differences in plasma LH concentrations but may be a consequence of differences in the control of LH secretion.     

A field study of kick injuries to the radius and tibia in 51 horses (2000–2010)

The objective of this study was to examine all kick injuries to the radius and tibia seen in an ambulatory setting over an 11-year period in order to determine factors affecting outcome. Medical records of 51 horses seen for a kick injury to the radius or tibia were reviewed. Signalment, physical examination findings, type of management, and outcome were evaluated. There was a significant association between the presence of bony crepitus and a lameness score of ≥ 4/5 and a poor outcome. There was no relationship between signalment and outcome, but significantly more Thoroughbred/Thoroughbred cross horses were affected than any other breed. There was no detected relationship between the type of management and outcome; however, most (81%) horses were managed on stall rest. Horses with bony crepitus or with a lameness score of ≥ 4/5 were at an increased risk for euthanasia.     

Effect of a soluble polysaccharide (carboxy methyl cellulose) on the physico‐chemical conditions in the gastrointestinal tract of broilers

1. The effects of an indigestible soluble polysaccharide (carboxy methyl cellulose: CMC) on broiler performance (body weight gain, food and water intake) and on chyme characteristics (moisture content, viscosity, pH, osmolality and retention time) in broilers were studied.

2. In semi‐synthetic diets 0, 5.0 and 10.0 g/kg of cellulose was replaced by CMC on weight basis. These diets were fed to male broilers from 3 to 5 weeks of age.

3. When 10.0 g/kg CMC was included in the diet, food intake and body weight gain were reduced, compared to the 0, and 5.0 g/kg CMC diets. Food:gain ratio and water intake were increased at each CMC concentration. The significant quadratic response showed an increased response per 5.0 g/kg dietary CMC at the higher CMC concentration.

4. The viscosity in the supernatant of the chyme was linearly increased in all intestinal segments by CMC. A quadratic increase was observed in the crop. In the lower ileum, differences between the 5.0 and 10.0 g/kg CMC diets were not significant.

5. CMC increased the mean retention time of chromium in the duodenum and in the upper jejunum, and reduced the maximal rate of marker excretion. The transit time (first appearance of the marker in the excreta), however, was significantly reduced at the highest CMC concentration.

6. The osmolality of the intestinal fluid decreased less as the chyme moved from the duodenum into the lower ileum, with increasing concentrations of CMC.

7. The ileal pH was reduced linearly by the CMC content of the diet.

8. Based on a higher moisture content of the chyme in the CMC‐fed birds, and the higher jejunal and ileal osmolarities in those birds, it was concluded that the efficiency of both digestion and absorption was reduced by CMC inclusion in broiler diets.     

Effect of clenbuterol on beta‐adrenoceptors and adenylate cyclase activity in smooth muscle and epithelium of the trachea of calves

Summary

A potent ß‐agonist (clenbuterol) was administered perorally to young calves for 50 days. After this period the animals were slaughtered and ß‐adrenoceptor density, ligand affinity, and basal and stimulated adenylate cyclase activities were studied in smooth muscle and epithelium of the trachea. Although the density of lung ß‐adrenoceptors was down regulated by clenbuterol, cAMP production remained constant (epithelium) or even increased (smooth muscle). Therefore desensitization of ß‐adrenoceptors in the trachea was not observed. This might be a reason for the effectiveness of long‐term treatment with ß‐agonists.     

Effects of the sex‐linked dwarf gene (dw) on skeletal muscle cellularity in broiler chickens

1. The number and size of muscle fibres and the DNA concentration in m. pectoralis superficialis of normal (Dw⁺ / ‐ ) and dwarf (dw/ ‐ ) White Plymouth Rock females were investigated at the ages of 9 and 52 weeks.

2. Live weight and total meat was reduced by 37.4 and 42.8% in dw/ ‐ as compared with Dw⁺/‐ females at the age of 9 weeks. The suppressive effect of the dwarf allele on the weight of m. pectoralis superficialis was 40.6% (67.8 v. 40.3 g in Dw⁺ / ‐ and dw/ ‐ genotypes). This reduction in weight was accompanied by a similar decrease of DNA content (28.8 v. 17.1 mg, i.e. 40.6%), a decrease in number of muscle fibres (829 × 10³ v. 654 × 10³, i.e. 21.2%) and fibre diameter (30.80 v. 28.95 μm, i.e. 6.0%). In mature hens, the differences between genotypes Dw⁺ / — and dw / ‐ were slightly smaller.

3. The different relationships between the muscle growth traits studied are discussed.     

The effects of feeding regime and stocking rate on the performance of medium‐bodied layers in the humid tropics

1. The effects of housing laying hens 1 or 2 per cage (1 452 or 726 cm² /bird), and three feeding regimes (ad libitum, 70% ad libitum and 6 days/ week) were investigated.

2. With 2 birds/cage egg production and food utilisation were adversely affected, but there were no significant effects on egg weight, food consumption, shell thickness, body‐weight change, mortality and abdominal fat.

3. Food restriction significantly increased body‐weight loss and decreased egg production, food consumption, final body weight and abdominal fat, but had no significant effect on egg weight, shell thickness and mortality. The effect on food utilisation was inconsistent.

4. There were significant interactions between feeding regime and stocking rate for egg weight and final body weight.

5. It is suggested that in the humid tropics birds caged singly could be fed at 70% ad libitum while those caged in pairs should be fed ad libitum to avoid multiple stress.