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1.
Taylor WP Roeder PL Rweyemamu MM Melewas JN Majuva P Kimaro RT Mollel JN Mtei BJ Wambura P Anderson J Rossiter PB Kock R Melengeya T Van den Ende R 《Tropical animal health and production》2002,34(6):471-487
In January 1997, Tanzania requested international assistance against rinderpest on the grounds that the virus had probably entered the country from southern Kenya. Over the next few months, a variety of attempts were made to determine the extent of the incursion by searching for serological and clinical evidence of the whereabouts of the virus. At the clinical level, these attempts were hampered by the low virulence of the strain, and at the serological level by the lack of a baseline against which contemporary interpretations could be made. Once it became apparent that neither surveillance tool was likely to produce a rapid result, an infected area was declared on common-sense grounds and emergency vaccination was initiated. The vaccination programme had two objectives, firstly to prevent any further entry across the international border, and secondly to contain and if possible eliminate rinderpest from those districts into which it had already entered. On the few occasions that clinical rinderpest was subsequently found, it was always within this provisional infected area. Emergency vaccination campaigns within the infected area ran from January to the end of March 1997 but were halted by the onset of the long rains. At this time, seromonitoring in two districts showed that viral persistence was still theoretically possible and therefore a second round of emergency vaccination was immediately organized. Further seromonitoring then indicated a large number of villages with population antibody prevalences of over 85%. These populations were considered to have been `immunosterilized'. Although no clinical disease had been observed in them, it was decided to undertake additional vaccination in a group of districts to the south of the infected area. Serosurveillance indicated that rinderpest could have been present in a number of these districts prior to vaccination. Serosurveillance in 1998 suggested that numerous vaccinated animals had probably moved into districts outside the infected and additional vaccination areas, but did not rule out the continued presence of field infection. 相似文献
2.
Wambura PN Meers J Kattenbelt JA Gould AR Spradbrow PB 《Veterinary research communications》2007,31(1):105-112
A single-tube RT-PCR technique generated a 387 bp or 300 bp cDNA amplicon covering the F0 cleavage site or the carboxyl (C)-terminus of the HN gene, respectively, of Newcastle disease virus (NDV) strain I-2. Sequence analysis was used to deduce the amino acid sequences of the cleavage site of F protein and the
C-terminus of HN protein, which were then compared with sequences for other NDV strains. The cleavage site of NDV strain I-2
had a sequence motif of 112
RKQGRLIG119, consistent with an avirulent phenotype. Nucleotide sequencing and deduction of amino acids at the C-terminus of HN revealed
that strain I-2 had a 7-amino-acid extension (VEILKDGVREARSSR. This differs from the virulent viruses that caused outbreaks of Newcastle disease in Australia in the 1930s and 1990s, which
have HN extensions of 0 and 9 amino acids, respectively. Amino acid sequence analyses of the F and HN genes of strain I-2
confirmed its avirulent nature and its Australian origin. 相似文献
3.
I–2 is an avirulent strain of Newcastle disease virus. During establishment of the I-2 strain master vaccine seed, a series of selection procedures was carried out at 56°C in order to enhance heat resistance. This master seed is used to produce a working seed, which is then employed to produce
the vaccine. These two passages are done without further heat selection; however, it is not known how rapidly and to what
extent thermostable variants would be lost during further passage. The study was therefore conducted to determine the effect
of passage on thermostability of strain I-2. The virus was serially passaged and at various passage levels samples were subjected
to heat treatment at 56°C for 120 min. The inactivation rates for infectivity and haemagglutinin (HA) titres were assayed by use of chicken embryonated
eggs and HA test, respectively. Thermostability of HA and infectivity of I-2 virus were reduced after 10 and 5 passages, respectively,
without heat selection at 56°C. These results suggest that 5 more passages could be carried out between the working seed and vaccine levels without excessive
loss of thermostability. This would result in increased vaccine production from a single batch of a working seed. 相似文献
4.
A rapid biological assay based on incubation time has been developed for determination of the potency of Newcastle disease
virus strain I-2 vaccine. It is based on the observation that the interval between inoculation and the first detection of
haemagglutinin (HA) depends on the titre of the vaccine inoculated. Chicken embryonated eggs were inoculated with different
titres (109, 106 and 103 EID50/0.1 ml) of vaccine and incubated for 24 h. At hourly intervals, 5 eggs from each vaccine titre were tested for the presence
of HA. The results showed that the HA activity was detected from 5, 11 and 15 h after inoculation with vaccine doses of 109, 106 and 103 EID50, respectively. On the basis of these results it is suggested that if there is no HA detected from 5 to 11 h after inoculation
of eggs with the vaccine virus, the vaccine should not be used to vaccinate chickens as it might have an infectivity titre
of less than 106 EID50/0.1 ml, which is equivalent to the recommended single chicken dose. It is concluded that measuring the time between inoculation
of the vaccine virus and the onset of HA activity might provide an estimate of the titre of the vaccine within 24 h. 相似文献
5.
Wambura PN 《Tropical animal health and production》2009,41(2):149-152
The efficacy of green-coloured (GC) I-2 Newcastle disease vaccine was determined in the present study. I-2 vaccine was mixed
with a green coloured dye and stored at 4°C for 6 months while assayed for the virus infectivity at a monthly interval. Chickens
were vaccinated with the GC vaccine by eye drop. Serum samples were collected from all birds before and after vaccination
at weekly interval for 4 weeks and tested for haemagglutination-inhibition (HI) antibody against Newcastle disease virus (NDV). These chickens were challenged with NDV virulent strain four weeks after vaccination. The results showed that there
was no difference between the infectivity titres of GC and uncoloured vaccines. However, chickens vaccinated with GC vaccine
produced higher HI antibody titres than chickens vaccinated with uncoloured vaccine. Results from the challenge trial showed
that all vaccinated chickens survived whereas all unvaccinated chickens died. The findings from this study have shown that
the GC vaccine is safe and produced protective antibodies against NDV in vaccinated chickens.
Wambura, P. N., 2008. Protective antibody response produced by the chickens vaccinated with green coloured thermostable Newcastle
disease virus. Tropical Animal Health and Production. 相似文献
6.
The study was conducted to prepare and evaluate the use of autogenous vaccine from Avibacterium paragallinarum (strain Tan 1-05) in layer chickens. The results showed that all chickens vaccinated with autogenous vaccine with 108 CFU/mL in aluminum phosphate gel developed MAT antibodies (GMT of 2.8 log2 to 5.3 log2) against A. paragallinarum infection. Moreover, the results indicated that all chickens (n = 6) selected from vaccinated chickens were protected against A. paragallinarum infection after challenge. No A. paragallinarum was isolated from these chickens. Nevertheless, all unvaccinated chickens did not develop antibodies, and all selected unvaccinated
chickens (n = 6) showed clinical signs consistent with infectious coryza (IC) where two of them died from the disease after challenge.
The findings from the present and previous studies showed that the development of an inactivated IC vaccine from local strains
if optimized and adopted may be the best possible way of controlling this economically important poultry disease. 相似文献
7.
Wambura PN 《Tropical animal health and production》2009,41(2):205-208
Antibody response produced by Newcastle disease virus (NDV, strain I-2) when given orally through oiled rice to chickens was determined. Serum samples were collected before and
at a weekly interval for 28 days after vaccination and tested for haemagglutination inhibition (HI) antibody to NDV. The results
showed 7 days after vaccination HI antibody titre log2 was 3.8. Moreover, 14 and 28 days after vaccination HI antibody titre log2 reached 6.5 and 8.0, respectively. All unvaccinated chickens were negative to NDV antibody throughout the study. Significant
finding from the present study is that 7 days after vaccination chickens had produced protective antibody against NDV; this
is in contrast to previous studies. Therefore, I-2 vaccine coated on the oiled rice is efficacious as it protects chickens
from challenge with NDV.
Wambura, P. N., 2008. Oral vaccination of chickens against Newcastle disease with I-2 vaccine coated on oiled rice. Tropical Animal Health and Production. 相似文献
8.
9.
Antibody responses in indigenous village and commercial chickens vaccinated with 12 thermostable Newcastle disease (ND) vaccine and protection levels against challenge with a virulent field isolate were determined. The antibody response of village chickens vaccinated by eye drop revealed that 30, 60 and 90 days after primary vaccination, the mean log2 HI titres were 6.1, 5.4 and 3.6, respectively, whereas for commercial chickens, the antibody response after 14, 30 and 90 days were 8.2, 5.1 and 4.2, respectively. Village chickens vaccinated orally via drinking water had mean log2 HI titres of 3.4 after 30 days. After booster vaccination, the mean HI titre was 5.4 and 3.3 after 30 and 60 days post-secondary vaccination (i.e. 60 and 90 days after primary vaccination). Antibody response of mean log2 HI titres of 2.6 was recorded 30 days after primary vaccination orally through food; 30 and 60 days after secondary vaccination (i.e. 60 and 90 days after primary vaccination), mean log2 HI titres were 5.3 and 3.2, respectively. All commercial and village chickens vaccinated by eye drop survived the challenge trial whereas village chickens vaccinated through drinking water and food had protection levels of 80% and 60% 30 days after primary vaccination, respectively. However, 30 days after booster vaccination, the protection level was 100%. At 60 days after secondary vaccination, the protection level dropped again to 80% for chickens vaccinated orally. All control chickens used in the challenge trials developed clinical ND and died 3-5 days after inoculation with the virulent virus. Supported by laboratory findings, I2 strain of NDV seemed to be avirulent, immunogenic and highly protective against virulent isolates of NDV. It may be a suitable vaccine to use in village chickens to vaccinate them against ND in rural areas. 相似文献
10.
Alexanda Mzula Selemani N. Masola Christopher J. Kasanga Philemon N. Wambura 《Tropical animal health and production》2014,46(5):711-716
Fowlpox virus (FPV) is one example of poultry viruses which undergoes recombination with Reticuloendotheliosis virus (REV). Trepidation had been raised, and it was well established on augmented pathogenicity of the FPV upon integration of the full intact REV. In this study, we therefore intended at assessing the integration of REV into FPV genome of the field isolates obtained in samples collected from different regions of Tanzania. DNA extraction of 85 samples (scabs) was performed, and FPV-specific PCR was done by the amplification of the highly conserved P4b gene. Evaluation of FPV–REV recombination was done to FPV-specific PCR positively identified samples by amplifying the env gene and REV long terminal repeats (5′ LTR). A 578-bp PCR product was amplified from 43 samples. We are reporting for the first time in Tanzania the existence of variant stains of FPV integrated with REV in its genome as 65 % of FPV identified isolates were having full intact REV integration, 21 % had partial FPV–REV env gene integration and 5 % had partial 5′ LTR integration. Despite of the fact that FPV–REV integrated stains prevailed, FPV–REV-free isolates (9 %) also existed. In view of the fact that full intact REV integration is connected with increased pathogenicity of FPV, its existence in the FPV genome of most field isolates could have played a role in increased endemic, sporadic and recurring outbreaks in selected areas in Tanzania. 相似文献