East coast fever: Further laboratory investigations on the use of rabbits as vehicles for infecting ticks with theilerial piroplasms

Summary A series of experiments was carried out in which attempts were made to achieve maximum survival ofTheileria parva-infected bovine erythrocytes in inoculated rabbits. By varying the treatment of the rabbits and of the erythrocytes and by altering the route of inoculation, it was finally shown that the best and most consistent results could be obtained by the intravenous inoculation of 20 ml of infected bovine blood into splenectomised rabbits. When nymphalRhipicephalus appendiculatus ticks were fed on such rabbits, the resultant adult ticks showed highTheileria parva infection rates in their salivary glands.

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Sumario Se llevaron a cabo una serie de experimentos tendientes a lograr el máximo de supervivencia de eritrocitos bovinos infectados conTheileria parva, en conejos inoculados. Variando el tratamiento de los conejos y eritrocitos, como también la ruta de inoculación, se demostró finalmente, que el resultado mejor y más consistente se obtuvo con la inoculación de conejos esplenectomizados con 20 ml de sangre infectada de bovino, via intravenosa.

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Résumé Une série d'expériences a été conduite pour déterminer le moyen le plus s?r d'assurer chez le lapin le maximum de survie auxTheileria parva d'érythrocytes de bovins infectés. En variant le traitement du lapin et des érythrocytes de boeufs, ainsi que les voies d'inoculation, les résultats les meilleurs et les plus réguliers ont été obtenus par inoculation intraveineuse de 20 ml de sang de bovin infecté à des lapins préalablement splénectomisés. Les nymphes deRhipicephalus appendiculatus nourries sur ces lapins donnent des tiques adultes dont les glandes salivaires sont fortement infectées parT. parva.

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On ODA secondment from the ARC Institute for Research on Animal Diseases, Compton, Nr. Newbury, Berkshire, UK (ODA Research Project R2396).

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On ODA secondment from the Central Veterinary Laboratory, New Haw, Weybridge, Surrey, UK.

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FAO Animal Health Officer.

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Project supported by the United Nations Development Programme with the Food and Agriculture Organization of the United Nations as the Executing Agency, in co-operation with the East African Community. The Project is also supported by the Overseas Development Administration of the United Kingdom (Research Projects R2396 and R2494), the United States Department of Agriculture, the International Atomic Energy Agency and the Pfizer Corporation.     

Laboratory diagnosis, epizootiology, and efficacy of marker vaccines in classical swine fever: a review

Detection of classical swine fever virus (CSFV) can be achieved by a range of assays of which the most commonly used are: immunohistochemical and virus culture techniques. New developments have enabled the detection of viral proteins by enzyme-linked immunosorbent assays (ELISAs) and the detection of the viral genome by RT- PCR. So far, laboratory findings show that the latter assays may supplement or replace the conventional techniques in the near future. The detection of serum antibody against structural and non-structural proteins of CSFV has been improved by developments in recombinant DNA techniques and has lead to a range of ELISAs. Although the characteristics of these ELISAs are excellent, positive results still need to be confirmed in the virus neutralization test. The available amount of sequence data enables diagnosticians to type strains of CSFV as different by comparing several parts of the genome. In some cases, this can provide conclusive evidence if a primary or secondary outbreak has been detected. Increased efforts focused on the retrieval of relevant data on the introduction of CSFV in a pig holding and the spread of CSFV in- and between pig holding(s) has generated more insight into the epizootiology of the disease. A successful control and eradication programme for classical swine fever (CSF) can consist of zoosanitary measures and/or vaccination. The latter can compromise the export of live pigs and pig products considerably unless marker vaccines have been used. Several studies were performed to determine the efficacy of an E2 subunit vaccine and live recombinant vaccine candidates. Firstly, we determined the 95% protective dose of an E2 subunit vaccine at 32 microg E2 per dosage after a single application. Further studies with a single administration of the subunit vaccine showed that: the vaccine was stable for a prolonged period after production, was able to reduce horizontal and vertical transmission of CSFV among vaccinated pigs, and provided protection for at least 6 months. An E(rns) antibody discriminatory assay was developed for use in combination with the subunit vaccine. Evaluation of the E(rns) ELISA showed that the sensitivity of the assay was lower than but that the specificity was equal to that of existing antibody assays. Two live recombinant marker vaccines were evaluated for the induction of clinical protection and reduction of transmission of CSFV shortly after vaccination. Results showed that these vaccines provided good clinical protection 1 week after a single vaccination. Research has shown that marker vaccines can be used in the future to support the control and eradication of CSFV.     

Epidemiology of Potomac horse fever: an investigation into the possible role of non-equine mammals

A serological study of antibodies to Ehrlichia risticii was carried out on 10 species of wild and domestic mammals found on or near 21 horse farms in an area of the USA in which Potomac horse fever is endemic. No antibodies were found in 133 peridomestic rodents (Norway rats and house mice), nor in 108 wild rodents (white-footed mice and meadow voles) captured on farms. Three of the six domestic animal species examined, cats, pigs and a goat, showed serological evidence of exposure to E risticii. Seropositive animals were detected on three of the 21 premises. The eight seropositive cats (of 48 cats tested) were on two farms, and the three seropositive pigs (of 14 tested) were all on one farm which lay some 3 km from where the one seropositive goat (of three tested) was found. None of the 79 dogs, 75 cattle and seven sheep tested had antibodies to E risticii. The significance of these findings is discussed in the light of current understanding of the transmission of Potomac horse fever and of the epidemiology of other related ehrlichial diseases.     

Haemorrhagic bowel syndrome in dairy cattle: possible role of Clostridium perfringens type A in the disease complex

A survey based on clinical, pathological and microbiological investigations was performed on 11 Brown Swiss cattle affected with depression, anorexia, agalaxia, ruminal hypomotility, abdominal pain and melaena. In eight animals, macroscopical lesions consisted in haemorrhagic enteritis in the small intestine. Seven of eight isolates from tissue samples were identified as Clostridum perfringens type A, and four were identified as C. perfringens type A with the beta2 toxin gene. Based on these observations, animals were considered affected with haemorrhagic bowel syndrome.     

The role of indigenous wild, semidomestic, and exotic birds in the epizootiology of velogenic viscerotropic Newcastle disease in southern California, 1972-1973.

During an epornitic of velogenic viscerotropic Newcastle disease (VVND) in southern California, free-flying wild birds, captive and free-ranging semidomestic birds, and exotic birds were collected from the quarantine area to determine their role in the epizootiology of the disease. The VVND virus was isolated from 0.04% of 9,446 free-flying wild birds, 0.76% of 4,367 semidomestic birds, and 1.01% of 3,780 exotic birds examined. Three house sparrows and 1 crow directly associated with infected poultry flocks were the only free-flying wild birds from which VVND virus was isolated. Among semidomestic species, ducks, quail, chukars, pheasants, peafowl, pigeons, and doves were found to be infected. Psttacines, pittas, and toucans accounted for 92% of the VVND virus isolations from exotic birds. In addition, domestic Newcastle disease virus (NDV) was isolated from 0.29% of the free-flying wild birds, from 1.65% of the semidomestic birds, and from 0.19% of the exotic birds collected. Hemagglutination-inhibition against domestic NDV was demonstrated in 0.24% of 3,796 wild bird serums, 8.28% of 2,004 semidomestic bird serums, and 3.90% of 231 exotic bird serums tested. Although few free-flying wild birds were infected with VVND virus in this epornitic, the isolation of domestic NDV strains from free-flying wild ducks and mourning doves suggests the potential for transportation of NDV over long distances by migratory birds.     

A possible role for Clostridium difficile in the etiology of calf enteritis

Clostridium difficile was investigated as a possible cause of enteritis in calves. The organism and its toxins (TcdA and TcdB), respectively, were found in 25.3% and 22.9% of stool samples from diarrheic calves. Culture positive samples were more likely than culture negative samples to be toxin positive. However, toxin positive stools were more common among nondiarrheic calves, but diarrheic calves were nearly twice as likely to be culture positive. Ribotype 078 was dominant among isolates. Salmonella sp. was isolated from both diarrheic and nondiarrheic calves, but large numbers of E. coli were found more commonly in diarrheic calves than in nondiarrheic animals. Prevalence rates for coronavirus and Cryptosporidium sp. were substantially higher in nondiarrheic calves than in diarrheic, but rates of detection of rotavirus and Giardia sp. were more nearly equal between groups. Lesions in naturally infected calves included superficial mucosal erosion with associated fibrinous exudates. Neutrophils and eosinophils infiltrated lamina propria. Large Gram-positive rods morphologically compatible with C. difficile were abundant in the colonic lumen and the organism was isolated by bacteriologic culture. Toxins were found throughout the colon. Purified toxins A and B (individually and conjointly) caused comparable lesions, as well as fluid accumulation, in ligated intestinal loops. Our findings are in substantial agreement with those of others [Rodriguez-Palacios, A., Stampfli, H.R., Duffield, T., Peregrine, A.S., Trotz-Williams, L.A., Arroyo, L.G., Brazier, J.S., Weese, J.S., 2006. Clostridium difficile PCR ribotypes in calves, Canada. Emerg. Infect. Dis. 12, 1730-1736; Porter, M.C., Reggiardo, C., Bueschel, D.M., Keel, M.K., Songer, J.G., 2002. Association of Clostridium difficile with bovine neonatal diarrhea. Proc. 45th Ann. Mtg. Amer. Assoc. Vet. Lab. Diagn., St. Louis, MO, U.S.A.] and add strength to a working hypothesis that C. difficile infection and the accompanying intoxication can manifest as diarrhea in calves. It seems clear that calves serve as multiplying hosts for this organism.     

Investigations into the possible role of Mycoplasma arginini in ovine respiratory disease

The inoculation of eight five- to seven-month-old sheep by the respiratory route with a culture of Mycoplasma arginini, administered simultaneously with or two days before a culture of Pasteurella haemolytica A2, did not lead to the pulmonary establishment of either organism. Minor lung changes found at slaughter seven days later were therefore considered not to have been induced by the inocula. Two other groups of seven sheep each were initially inoculated intratracheally with an ampicillin-treated lung lesion homogenate in which only M ovipneumoniae was detectable. After seven days one group was inoculated intranasally and intratracheally with mixed cultures of M arginini and P haemolytica A2, and one with P haemolytica A2 alone. In the M arginini-treated group pyrexia peaked earlier and one animal died, but no macroscopic or microscopic differences were apparent between the two groups at necropsy 10 to 11 days later; six sheep from each group had lung lesions indistinguishable from ovine atypical pneumonia. M arginini was isolated in high titre from the respiratory tract of two animals in the M arginini-treated group, including the sole fatality. However, an adventitious parainfluenza type 3 virus infection, identified in four animals from the M arginini-treated group and one from the other, may have been responsible for the inter-group clinical differences. It was concluded that the strain of M arginini used was capable neither of predisposing the lung to secondary invasion by P haemolytica A2, nor of exacerbating the pneumonia and effects elicited with M ovipneumoniae and P haemolytica.     

Elastase-producing microorganisms in horse lungs: their possible role in the pathogenesis of chronic pulmonary disease in the horse

Seventeen out of 21 horses had pulmonary microbial organisms which reached considerable numbers in seven cases. Elastase-producing microorganisms from the environment (Streptomyces species and to a lesser extent Bacillus species) constituted 22 per cent to 99 per cent (mean 79 per cent) of the total growth. There was a considerable number of microorganisms with in vitro-produced elastases which were not or only slightly affected by horse serum. There was no correlation between numbers of organisms and pulmonary histopathological findings thus the significance of these microorganisms in the pathogenesis of alveolar emphysema is unknown. The growth of a strain of Streptomyces collinus/diastatochromogus isolated from the lungs was suppressed by fresh horse serum but not by decomplemented horse serum. Complement activation in response to this organism could contribute to airway inflammation through the production of mediators.     

A study on the possible role of chymotrypsin in the aetiology of equine chronic obstructive pulmonary disease (COPD)

The chymotrypsin activity of seven batches of Micropolyspora faeni and of five batches of Aspergillus fumigatus culture extracts, prepared for inhalation challenge in horses, was assayed and was found to range between 0.29 and 1.45 units/mg protein and 0.02 and 0.20 units/mg protein respectively. Horses affected with chronic obstructive pulmonary disease (COPD) were challenged with two batches of each antigen which had different chymotrypsin activities and no significant correlations were found between the degree of response to challenge and the chymotrypsin activity of the antigens. Inhalation of two doses of nebulised, purified chymotrypsin over 4 days did not induce signs of respiratory disease in COPD-affected horses. However, repeated chymotrypsin inhalations after an interval of 3 weeks caused an exacerbation of signs of COPD in one horse. These studies suggest that, although repeated inhalation of purified chymotrypsin may induce respiratory hypersensitivity in horses, the chymotrypsin-like enzymes of M. faeni and A. fumigatus do not play a major role in the precipitation of clinical signs of equine COPD.     

Striped mice, Rhabdomys pumilio, and other murid rodents as hosts for immature ixodid ticks as in the Eastern Cape Province

Striped mice, Rhabdomys pumilio, were trapped over a period of 17 months in the Thomas Baines Nature Reserve, and placed in cages, over water, until all the ticks they harboured had detached. The mice were then returned to the reserve. Four ixodid tick species were recovered from the mice of which the larvae and nymphs of Rhipicephalus follis and Rhipicephalus simus were the most numerous. Most larvae of R. follis detached from mice trapped from March to July, and most nymphs in March and from June to September. Most larvae of R. simus detached from mice trapped from December to March, and most nymphs from January to March and during May and June. Seven ixodid tick species were collected from striped mice, house rats, Rattus rattus, vlei rats, Otomys spp. and Praomys sp. captured in the vicinity of human dwellings or animal holding facilities in the Grahamstown district. The striped mice captured in the Thomas Baines Reserve harboured considerably larger numbers of ticks than any of the rodent species in the more urbanized localities.     

The role of common starlings (Sturnus vulgaris) in the epidemiology of bacterial, potentially human pathogenic, disease agents

Since a long time a public garden in Basel is known as a site for overnight accommodation and assembly of starlings. The birds cause an immense faecal contamination of the park and the neighbouring district. A nursery and a primary school are directly affected. To evaluate the health risk coming from the starlings droppings for the population, particularly for the children and to assess the role of starlings in the transmission of diseases to humans and in the epidemiology of human diseases the presence of human bacterial pathogens in the faeces of starlings was determined. Some of the isolated strains were further typed and compared to strains of human origin. C. jejuni, L. monocytogenes and C. psittaci were most often found. The typing of some C. jejuni and L. monocytogenes isolates showed a great variety of geno-, sero- respectively phage types that did not belong to the strains most often found in isolates of human origin. Starlings can harbour human pathogens and therefore a potential risk of infection comes from their droppings. It seems however rather improbable, that these birds present a constant direct source of infection for human beings.     

Glucose homeostasis and the enteroinsular axis in the horse: A possible role in equine metabolic syndrome

One of the principal components of equine metabolic syndrome (EMS) is hyperinsulinaemia combined with insulin resistance. It has long been known that hyperinsulinaemia occurs after the development of insulin resistance. But it is also known that hyperinsulinaemia itself can induce insulin resistance and obesity and might play a key role in the development of metabolic syndrome. This review focuses on the physiology of glucose and insulin metabolism and the pathophysiological mechanisms in glucose homeostasis in the horse (compared with what is already known in humans) in order to gain insight into the pathophysiological principles underlying EMS. The review summarizes new insights on the oral uptake of glucose by the gut and the enteroinsular axis, the role of diet in incretin hormone and postprandial insulin responses, the handling of glucose by the liver, muscle and fat tissue, and the production and secretion of insulin by the pancreas under healthy and disrupted glucose homeostatic conditions in horses.     

Pathophysiology of the periparturient egg rise in sheep: a possible role for IgA.

The relationship between anti-parasite IgA antibody levels in plasma and the periparturient egg rise in sheep was investigated. Ostertagia circumcincta larvae (5000 third stage larvae three times weekly) were administered to three groups of seven adult immune ewes from 12 weeks before until three weeks after lambing (group 1) or from six (group 2) or 14 (group 3) weeks before until three weeks before lambing. Seven additional ewes were not challenged (group 4 controls). Ewes in groups 1, 2 and 4 received anthelmintics 14 weeks before lambing. Challenge of the pregnant ewes with O circumcincta larvae resulted in substantial increases in faecal egg counts only during the periparturient period regardless of the larval dosing regimen. Furthermore, the periparturient rise in faecal egg counts was closely associated with a significant increase in anti-parasite IgA antibody levels in plasma. This rise in IgA antibody levels occurred at a time when IgA is transported from the gut to milk during early lactation. It is postulated that this may lead to a temporary reduction in abomasal antibody levels of ewes and hence permit the establishment of larvae and, or, the emergence and development of inhibited larvae and thereby lead to the periparturient rise in faecal egg count.     

The possible role of Ostertagia circumcincta, coccidiosis and dietary protein level in the development of swelling disease in Angora goat kids

A trial was carried out to investigate the possible role of Ostertagia circumcincta, coccidiosis and level of protein in the diet in the development of swelling disease in Angora goat kids. Eighty Angora goat kids were bought from 5 producers whose flocks had a history of swelling disease. These kids were kept in enclosures at Grootfontein Agricultural Development Institute near Middelburg (Eastern Cape) for the duration of the experiment. The animals received a combination of the following treatments: (a) high protein vs normal protein diet; (b) Ostertagia circumcincta infection or no O. circumcincta infection; (c) coccidial infection or no coccidial infection. Data recorded included weekly body weight, weekly total plasma protein levels (TPP), weekly faecal egg counts, weekly coccidial oocyst counts and haematology at Weeks 1, 5, 9, 13 and 16. The goats were also monitored daily for any clinical symptoms. There was no specific trend in any of the parameters measured among the different treatment groups at any stage during the experimental period. The goats were shorn during Week 10 of the experiment. On Monday 6 September 2004 (Week 12 of the study), 19 of the goats developed some subcutaneous oedema. The Saturday (4 September 2004) was rather hot (30 degrees C), followed by very cold rainy conditions (11 degrees C) on Sunday (5 September 2004). Twelve of the goats developed what can be described as little oedema, while 7 developed moderate oedema. The number of goats that developed oedema was fairly evenly distributed among the various treatment groups. As far as the specific treatments are concerned, more goats on the normal protein diet developed moderate oedema than the goats on the high protein diet. Body weights of goats that developed moderate oedema were lower throughout the experimental period than body weights of goats that developed little or no oedema, while TPP of goats that developed moderate oedema were lower from Week 5 of the study onwards. There were also no significant differences at any stage throughout the experimental period in faecal egg counts, faecal coccidial oocyst counts or any of the blood parameters between goats that developed moderate oedema, little oedema and those that did not develop any oedema. No goats developed full-blown swelling disease during the course of the experiment. It is possible that the treatments applied in this study are not inductive of the disease, or the effects of the treatments were not severe enough to induce swelling disease.     

Neocucumis kilburni sp. nov. (Echinodermata : Holothuroidea : Cucumariidae) from the east coast of South Africa,with a key to the genus Neocucumis

A new dendrochirotid holothuroid, Neocucumis kilbumi, is described from waters 50 meters deep, off the southern coast of KwaZulu-Natal, South Africa. It appears quite close to N. watasei (Ohshima) and N. sordidatus (Sluiter), both from the West Pacific and to N. atlanticus (Ludwig & Heding) from the Atlantic Ocean and the Mediterranean Sea. It differs from the former in the nature of the calcareous ring and the disc and the spire of the body wall tables, from N. sordidatus in the completeness of its deposits and the number of polian vesicles and from N. atlanticus in the presence of handles to the quadrilocular table discs. The new species increases to ten the number of species now classified in the genus Neocucumis. A key to all the species is included.