Studies on experimental Jembrana disease in Bali cattle. III. Pathology.

Experimental infection of Bali cattle (Bos sondaicus) with blood from a case of Jembrana disease caused a well-defined pathological response. The disease was generalized except for the central nervous system which did not show significant cellular reactive changes. Following a general lymphoreticular reaction in the first week (Phase 1), the predominant effect was an intense non-follicular proliferative response by reticulum (dendritic) cells and lymphoblastoid cells in lymphoid organs (Phase 2) and a similar infiltrative and proliferative process in liver, kidneys, adrenal medulla and elsewhere. In the kidneys, glomerular hypercellular swelling occurred which was associated with uraemia. Pulmonary alveolar cells reacted strongly to infection by swelling and proliferation especially in the anterior lobes. Mononuclear cell infiltration accompanied this response. In lymph nodes and spleen, a marked lymphoid follicular reaction and plasma cell formation developed from the fifth week of infection (Phase 3). The cytology and histological distribution of proliferative changes in the lymphoid system suggests that, during the acute phase of the disease, a predominantly T lymphocytic reaction takes place which may be associated with transient immunosuppression. Residual lesions occurred up to day 60 post-infection. In all affected tissues pleomorphic basophilic, intracytoplasmic inclusions occurred, especially from the second week until about the fifth week of infection, but persisted in small numbers for more than 2 months. By light microscopy both minute basophilic granular forms (Type 1) and large intravascuolar (Type 2) inclusions were consistently found in reticular cells, lymphoblasts, macrophages including Kupffer cells, pulmonary alveolar cells and occasionally in vascular endothelium. These structures appear to be of diagnostic value.     

Studies on experimental Jembrana disease in Bali cattle. II. Clinical signs and haematological changes

The clinical and haematological changes which occurred in 18 Bali cattle (Bos javanicus) experimentally infected with Jembrana disease are described. The major clinical signs were an elevated rectal body temperature persisting for 7 days (range 5 to 12 days), lethargy, anorexia, enlargement of the superficial lymph nodes, a mild ocular and nasal discharge, diarrhoea with blood in the faeces and pallor of the mucous membranes. Not all of these changes occurred in all affected cattle. The major haematological changes included leucopenia, lymphopenia, eosinopenia and a slight neutropenia, a mild thrombocytopenia, a normocytic normochromic anaemia, elevated blood urea concentrations and reduced total plasma protein. The mortality rate in the experimentally infected cattle was 17 per cent. The similarity of Jembrana disease to malignant catarrhal fever and to diseases of cattle associated with Ehrlichia is discussed.     

Vaccination reduces the viral load and the risk of transmission of Jembrana disease virus in Bali cattle

The efficacy of a tissue-derived vaccine, which is currently used in Indonesia to control the spread of Jembrana disease in Bali cattle, was determined by quantifying the viral load in plasma following experimental infection with Jembrana disease virus. Virus transmission is most likely to occur during the acute phase of infection when viral titers are greater than 10⁶ genomes/ml. Vaccinated cattle were found to have a 96% reduction in viral load above this threshold compared to control cattle. This would reduce the chance of virus transmission as the number of days above the threshold in the vaccinated cattle was reduced by 33%. Viral loads at the onset and resolution of fever were significantly lower in the vaccinated cattle and immune function was maintained with the development of antibody responses to Env proteins within 10-24 days post challenge. There was, however, no significant reduction in the duration of the febrile period in vaccinated animals. The duration and severity of clinical parameters were found to be variable within each group of cattle but the quantification of viral load revealed the benefits of vaccinating to reduce the risk of virus transmission as well as to ameliorate disease.     

Factors in the resistance of rats to re-infection and super-infection by Clonorchis sinensis

Rats develop resistance to re-infection by Clonorchis sinensis while humans do not. We investigated factors involved in the development of resistance to re-infection and super-infection in rats. Sprague–Dawley rats were infected by C. sinensis metacercariae and treated with praziquantel, then re-infected after immune modulation. The rats were also subjected to super-imposed infection after primary infection. Resistance to re-infection was observed by lowered rates of worm recovery after various durations from treatment; 1% at 5days and 24.4% at 11months vs 56.2% in the control. Similar significant resistance was observed in the super-infected rats after 3weeks of primary infection. The re-infected or super-infected worms grew very slowly and remained immature. Resistance disappeared in immune-suppressed and nude rats but not in splenectomized rats. Immunization with antigens of C. sinensis produced no resistance. Local tissue reaction and immune response in the infected bile duct may play an important role in the resistance, although the crowding effect may also be implicated in resistance in super-infected rats.     

Studies on hypersensitivity. I. Delayed and Arthustype skin reactivity to protein conjugates in guinea pigs

A study has been made of the immunization of guinea pigs with proteins conjugated with picryl, acetyl and ethoxymethylene-phenyloxazolone groups. Immunization by means of complexes of these substances with anti-protein and anti-hapten antisera have also been studied. Antibody production, anaphylactic and Arthus-type sensitivity and delayed skin sensitivity to the conjugates, to the carrier proteins and to unrelated proteins carrying the same haptenic group have been investigated.

Immunization with conjugates is found to be followed by the appearance of delayed hypersensitivity to the protein `carrier' in the absence of detectable antibodies against it, although antibodies are produced at that time against the haptenic group itself. Delayed hypersensitivity to the haptenic group has not been detected at any time: blocking it with specific antibody does not lead to the appearance of delayed sensitivity, but merely suppresses antibody formation against that group.

Pure delayed sensitivity has been produced against gelatin, both alone and as a conjugate with picryl. Conjugates with homologous serum proteins are shown to provoke only Arthus-type sensitivity and antibody against the haptenic group.

These findings are discussed in view of the light they may throw upon the relation of delayed hypersensitivity to antibody production and upon the process of immunization.

     

Streptomycin and chloramphenicol resistance genes in Escherichia coli isolates from cattle, pigs, and chicken in Kenya

The aims of this study were to determine the genetic basis of streptomycin and chloramphenicol resistance in 30 Escherichia coli isolates from food animals in Kenya and the role of plasmids in the spread of the resistance. Seven of the 29 streptomycin-resistant isolates harbored both the strA and strB genes. Twenty-one of isolates had the strA, strB, and aadA1 genes. The strA gene was disrupted by a functional trimethoprim gene, dfrA14 in 10 of the 21 isolates harboring the three streptomycin resistance genes. Physical linkage of intact strA and sul2 genes was found in two different plasmids from four isolates. Linkage of cassette-borne aadA1 and dfrA1 genes in class 1 integrons was found in two of the isolates. Chloramphenicol resistance was due to the gene catA1 in all the chloramphenicol resistant isolates. The strB, strA, and catA1 genes were transferable by conjugation and this points to the significance of conjugative resistance plasmids in the spread and persistence of streptomycin and chloramphenicol resistance in food animals in Kenya.     

Studies of quantitative parameters of virus excretion and transmission in pigs and cattle experimentally infected with foot-and-mouth disease virus

Foot-and-mouth disease virus (FMDV) can be spread by a variety of mechanisms and the rate of spread, the incubation period and the severity of disease depend on a multitude of parameters, including the strain of virus, the dose received, the route of introduction, the animal species and the husbandry conditions. More knowledge with regard to these parameters is urgently needed to improve resource-efficient disease control. This report describes detailed studies of FMDV load, excretion and transmission in pigs infected with FMDV O UKG 2001, O TAW 1997 and C Noville virus and in cattle infected with the O UKG 2001 virus to facilitate use of a "FMDV load framework" for the assessment of transmission risks. Virus replicated rapidly in pigs and cattle exposed by direct contact. The mean incubation period was around 3-4 days for cattle-to-cattle and 1-3 days for pig-to-pig transmission, depending on the intensity of contact. The results confirmed that a strong relation exists between dose and length of incubation period. Clinical disease was severe in pigs but relatively mild in inoculated cattle; contact infection of cattle appeared to increase the severity of lesions. FMDV RNA was recovered in nasal and mouth swabs from inoculated animals soon after they developed a viraemia and probably reflected the early production and excretion of virus. FMDV RNA in nasal and mouth swabs from contact animals could be detected several days before they showed other signs of infection, indicating the possibility of detecting exposed animals during the incubation period. FMDV RNA could also be detected in swab samples after the viraemic phase. This may have represented background environmental virus that had been trapped in the respiratory tract and mouth. Alternatively, it may have indicated a somewhat slower clearance or half-life of viral RNA or an extended low level of FMDV replication at these sites. The pattern of FMDV RNA concentrations in pigs was closely similar to that in cattle, but the amounts of FMDV RNA were higher.     

Histopathology of experimental Legionnaires' disease in guinea pigs,rhesus monkeys and marmosets

Guinea pigs, rhesus monkeys and marmosets were infected with L. pneumophila in small particle aerosols. Fever and acute fibrinopurulent pneumonia resulted. The lesions involved distal lung tissue only, spreading from terminal and respiratory bronchioles and producing heavy infiltration of alveoli by polymorphs and macrophages and widespread exudation of oedema fluid and fibrin. Lesions were not found in extra-pulmonary sites.     

Immunological experimental arthritis in pigs. I. Propagation dynamics of the attenuated strain of Aujeszky's disease virus in the pig organism and the humoral immunity formation.

Studies on the propagation dynamics of Aujeszky's disease virus and the formation of general and local joint immunity were to provide information explaining the mechanism of experimental rheumatoid arthritis in animals. It was shown that: Aujeszky's disease virus administered intramuscularly caused viremy on 3-4th day after its application and disappeared from the blood circulation on 5-6th day, introduced into the pig ankle joint, the virus was eliminated from the articular fluid two hours after injection, but it appeared again 3-7 days later probably due to the propagation in the cells of the synovial membrane, and that first parenteral administration of the virus induced the formation of neutralizing antibodies in low titer (5-10 units); application of the virus for the second time brought about a considerable increase of antibodies titer within 40-80 units.     

Immunological experimental arthritis in pigs. III. Inflammatory reactions in the brain of pigs immunized with the attenuated virus of Aujeszky's disease.

Histopathological brains and spinal cords of pigs were examined at different times of immunization with the virus of Aujeszky's disease (AD). Temporary inflammatory reaction was found to have the features of non-suppurative disseminated inflammation in the second week after the second virus dose had been given. Perivascular and subependymal lymphocytic infiltrations were observed and the focal multiplication of microglia.