A case of Newcastle disease virus infection in a female laboratory technician is reported for the first time in Malaysia. Infection was acquired by droplet infection of the eye while grinding infected chicken in the laboratory. The case was confirmed by isolation of Newcastle disease virus from an eye swab taken from the subject on the first day of clinical signs. A four-fold rise of haemagglutination-inhibition titre was shown when sera on the third day of infection and 15 days later were compared.
One-day-old chickens were transported from Australia to Malaysia and vaccinated orotracheally with an uninactivated vaccine prepared from avirulent Australian V4 strain of Newcastle disease virus (NDV). The vaccination regimes were as follows: group A, once, at 2 weeks old; group B, once, at 3 weeks old; group C, twice, at 2 and at 3 weeks old; group D, direct contact with groups A, B, and C; and group E, indirect contact with groups A, B, C, and D. Group F was unvaccinated controls. Challenge was with NDV virulent Ipoh AF 2240-226 strain, administered at 4 weeks old intramuscularly to 10 chickens in each group and orotracheally to 10 chickens in each group. The remaining chickens were challenged by contact with the inoculated chickens. Group mortalities following challenge were: A, 1/77; B, 1/34; C, 0/39; D, 0/45; E, 6/43; and F, 60/60.
An experimental oil emulsion Newcastle disease vaccine was evaluated for its efficacy in broiler chickens. A group of chickens vaccinated at one day old with a live lentogenic Newcastle disease vaccine and subsequently revaccinated at three and eight weeks old with the experimental oil emulsion vaccine showed satisfactory haemagglutination inhibition antibody response which persisted for 18 weeks. Between 90 and 100 per cent of the vaccinated chickens were protected when challenged with the velogenic viscerotropic Newcastle disease virus. Although the vaccinated chickens were protected against clinical disease, virus could be isolated from a number of birds. By day 10 to 12 after challenge all the chickens were free from Newcastle disease infection.
A cross-sectional serological survey of domestic animals in West Malaysia revealed that 25.5% of the animals examined had agglutinating antibodies to one or more antigens belonging to Leptospira interrogans. Significant prevalence of infection was observed in cattle (40.5%), buffaloes (31%) and pigs (16%). The Sejroe serogroup was shown to be the principal one involved in cattle and buffaloes, and to a lesser extent the Tarassovi and Pomona serogroups. Evidence of infection in domestic animals by strains bearing the other seven antigens appeared insignificant and was indicative of sporadic infection. A majority of the large (semi-intensive) cattle and buffalo farms demonstrated a high prevalence of leptospiral infection. In both species of domestic animals mentioned above, the prevalence of infection was significantly higher (P = 0.01) in the semi-intensive farms than in the smallholdings. Amongst cattle, the droughtmasters had the highest prevalence whilst the Kedah-Kelantan (an indigenous breed) had the lowest prevalence of leptospiral infection. In general, the temperate breeds of cattle had a significantly (P = 0.01) higher prevalence of infection than local breeds. Leptospiral infection in goats and sheep was shown to be sporadic, and the Pomona serogroup was the principal leptospiral serogroup involved in these small ruminants. The prevalence of infection in pigs was observed to decline during the study period, and it is suspected that pigs in West Malaysia are the maintenance host for serovar pomona whilst cattle are the maintenance host for serovar hardjo. Overall, it appears that domestic animals in Malaysia will play a bigger role in the epidemiology of leptospiral infection with the advent of sophisticated farming.
A cross-sectional bacteriological survey of cattle in West Malaysia revealed 14.4% (32/222) had leptospiral infection. Isolates were obtained from all except one herd with prevalence of infection in herds ranging from 0-44.8%. A small number of buffalo urine samples were examined and all of them were found to be negative. A leptospiral isolate obtained from a bovine kidney proved to be a new serovar of Leptospira interrogans and the name unipertama was assigned to it. Six other leptospiral serovars were isolated, namely canicola, australis, javanica, ballum, pomona and hardjo. All six serovars were isolated for the first time in cattle in Malaysia. Cattle in Malaysia appear to be the maintenance host for serovar hardjo. The presence of the other serovars in cattle was probably due to contact with the maintenance hosts, pigs for serovar pomona and rodents for the other three serovars. It appears that the epidemiology of leptospiral infection in cattle in Malaysia is similar to that reported overseas.
Hemagglutination activity, structural protein profiles and neutralization assays were used in a comparative study of bovine herpesvirus 1 strains from the U.S.A., Canada, Great Britain, Denmark and Malaysia with equine, feline and human herpesviruses in order to further characterize the bovine herpesvirus 1 hemagglutinin. Bovine herpesvirus 1 strains of different geographical origins all showed hemagglutinating activity for mouse erythrocytes; furthermore, feline herpesvirus 1 was also shown to hemagglutinate mouse erythrocytes. Analyses of partly purified viruses showed that a distinctive and specific polypeptides profile is associated with each species of herpesviruses used in our study; strains of bovine herpesvirus 1 from North America, Europe and Southeast Asia however, presented a remarkable similarity as to their electrophoretic protein patterns. A protein similar to the 97-kDa bovine viral hemagglutinin was not identified with the hemagglutinating feline herpesvirus. An important neutralization epitope on the bovine viral hemagglutinin was also not found on feline, equine and human herpesviruses but was identified on all bovine strains tested from North America, Europe and Southeast Asia stressing the importance of the bovine hemagglutinin for eventual prophylactic purposes.
This paper reviews the literature on leptospirosis in Malaysia from its first description in 1928 until the present day. Most of the early reports were on investigations of leptospirosis in wildlife and man and up-to-date, thirty-seven leptospiral serovars from thirteen serogroups have been bacteriologically identified. The thirteen serogroups are: Australis, Autumnalis Bataviae, Canicola, Celledoni, Grippotyphosa, Hebdomadis, Icterohaemorrhagiae, Javanica, Pomona, Pyrogenes, Sejroe and Tarassovi. Rats have been ascribed as the principal maintenance host of leptospires in Malaysia. However, serovars from the Pomona, Pyrogenes and Sejroe serogroups have yet to be isolated from rats. It is considered that the majority of leptospirosis cases in man were due to association of man with an environment where rats were plentiful. Recent investigations on domestic animals disclosed a high prevalence of infection in cattle and pigs and they were suspected as being the maintenance host for serovar hardjo and pomona respectively. There is ample scope for research in leptospirosis, particularly in the epidemiology and control of the disease in domestic animals. The strategy to control the infection in domestic animals and man in Malaysia is bound to be different from that of the temperate countries, basically due to the presence of a large number of leptospiral serovars in wildlife, further confounded by geographical and financial constraints.
A leptospiral isolate from a bovine kidney was found to be antigenically different from all previously recognized serovars of Leptospira interrogans based on the cross-agglutinin absorption test. The new serovar belongs to the Sejroe serogroup, and the name Leptospira interrogans serovar unipertama is proposed for it, with strain K2-1 as the reference strain.
The Australian, heat-resistant, a virulent V4 strain of Newcastle disease (ND) virus was selected for further heat resistance to give a variant designated V4-UPM. V4-UPM was sprayed on to food pellets which were fed to chickens in amounts calculated to give about 10(6) EID50 per chicken. Chickens vaccinated only once by feeding developed no haemagglutination-inhibition (HI) antibodies and were not protected against challenge with a viscerotropic velogenic strain of ND virus. Chickens given food pellet vaccine at 3 and 6 weeks of age developed HI antibodies and were substantially protected against parenteral and contact challenge with virulent ND virus. Similar protection was achieved when the V4-UPM vaccine was given intranasally on two occasions or when the vaccine virus was allowed to spread by contact from intranasally vaccinated chickens to nonvaccinated chickens. Heat resistant ND vaccine incorporated in food pellets may provide a method for protecting village chickens against ND in tropical countries.
The food pellet vaccine has been shown to be effective in trials conducted under laboratory and simulated field conditions. The village chickens vaccinated with the food pellet vaccine during the field trial were protected against virulent Newcastle disease virus. The efficacy of the food pellet vaccine in the field was evaluated by challenge trial in which 60 per cent protection was obtained, or by monitoring the incidence of Newcastle disease in vaccinated and unvaccinated birds. There was no report of Newcastle disease outbreaks in the vaccinated birds during the two-year period of the field trial. The ease in administering the food pellet vaccine makes it readily accepted by the farmers.
The nucleotide sequence of the haemagglutinin-neuraminidase (HN) gene of Newcastle disease virus (NDV) viscerotropic-velogenic strain AF2240 was determined by direct RNA sequencing and by sequencing RT-PCR products. It encodes a single open reading frame of 581 amino acids with a calculated Mr of 63.8 kDa. The predicted sequence contains five asparagine glycosylation sites. Comparison of the AF2240 HN protein sequence with 13 other previously published sequences showed 88% homology. This HN protein is unique because it lacked the Arg 403 residue which is present in all of the other strains and cannot be grouped under the proposed three size classes of HN proteins in NDV.
The nucleotide sequence of the haemagglutinin-neuraminidase (HN) glycoprotein gene of Newcastle disease virus (NDV) variant strain V4(UPM) was determined by direct genomic RNA sequencing and confirmed by cycle sequencing. The gene comprises 1996 nucleotides encoding a 615 amino acid protein of size 67.4 kDa. The nucleotide and amino acid sequences of this strain were compared with those of the parent strain V4(QUE). There are 16 nucleotide substitutions on V4(UPM), eight of which are silent mutations and another eliminated a potential Asn-linked glycosylation site in V4(UPM). In addition, an Arg (403) residue was shown to be absent in the variant strain. This deletion is thought to be significant because of its location in a highly conserved region of the HN protein.