L W Njagi

Pasteurella multocida in scavenging family chickens and ducks: carrier status, age susceptibility and transmission between species

Pasteurella multocida causes fowl cholera, a highly contagious and severe disease in chickens and water fowls. The disease is not well described in less intensive production systems, including scavenging family poultry production in developing countries. P. multocida was isolated from 25.9% of healthy-looking ducks and 6.2% of chickens from free-range family poultry farms and at slaughter slabs at market. On experimental infection with 1.2 to 2.0×108 organisms of the P. multocida type strain (NCTC 10322T), 12-week-old chickens expressed fowl cholera clinical signs significantly more times (372 signs) than those of 4-week-old, 8-week-old and 16-week-old chickens (173, 272 and 187 signs) and more signs were severe. In family ducks the 8-week-old birds expressed clinical signs significantly more times (188 signs) than those of the other age groups (117, 80, and 83 signs, respectively) and severe signs were more frequent. P. multocida transmitted from seeder birds (n=12) to sentinel birds (n=30), which developed clinical signs, and in some cases lesions of fowl cholera allowed bacterial re-isolation, whether infected ducks served as seeders for chickens or chickens served as seeder for ducks. This study has documented the occurrence of P. multocida among healthy-appearing family poultry in a tropical setting, and demonstrated that age susceptibility is highest in 12-week-old family chickens and 8-week-old family ducks when challenged with a low-virulent strain of P. multocida. It has further demonstrated that cross-transmission of fowl cholera may happen between family ducks and chickens, and vice versa.

Effect of Immunosuppression on Newcastle Disease Virus Persistence in Ducks with Different Immune Status

This study was carried out to verify the possibility that ducks are sources of Newcastle disease (ND) virus infection for chickens in mixed flocks. Immunosuppressed (IS) and non immunosuppressed (NIS) birds, at three different antibody levels (medium, low and absent) were used; the titres having been induced through vaccination, and Immunosuppression done using dexamethazone. Each of the 3 respective groups was further divided into 2 groups of about 12 ducks each: one challenged with velogenic ND virus; the other not challenged. Selected ducks from all groups had their antibody titres monitored serially using hemagglutination inhibition test, while two birds from each of the challenged groups were killed and respective tissues processed for ND viral recovery, using chicken embryo fibroblasts. In general, antibody titres of IS and NIS challenged ducks were significantly higher than their unchallenged counterparts (P < 0.05). Non-challenged pre-immunised ducks had a progressive decrease in antibody levels; non-immunised ducks did not seroconvert. Newcastle disease virus was isolated from livers and kidneys of the challenged ducks throughout the experimental period; indicating a possibility of viral excretion, especially when the birds are stressed. It, therefore, provides another possible model of viral circulation within mixed flocks.

Time-course investigation of infection with a low virulent Pasteurella multocida strain in normal and immune-suppressed 12-week-old free-range chickens

Twelve-week-old indigenous chickens, either immune-suppressed using dexamethasone (IS) or non-immune-suppressed (NIS), were challenged with a low virulent strain, Pasteurella multocida strain NCTC 10322T, and developed clinical signs and pathological lesions typical of chronic fowl cholera. NIS birds demonstrated much more severe signs of fowl cholera than IS birds. With few exceptions, signs recorded in IS and NIS birds were of the same types, but significantly milder in the IS birds, indicating that immune suppression does not change the course of infection but rather the severity of signs in fowl cholera. P. multocida signals by fluorescent in situ hybridization (FISH) were observed between 1 h and 14 days in the lungs, trachea, air sacs, liver, spleen, bursa of Fabricius and caecal tonsils, while signals from other organs mostly were observed after 24 h. More organs had FISH signals in NIS birds than in IS birds and at higher frequency per organ. Many organs were positive by FISH even 14 days post infection, and it is suggested that these organs may be likely places for long-term carriage of P. multocida following infection. The present study has demonstrated the spread of P. multocida in different tissues in chickens and distribution of lesions associated with chronic fowl cholera, and pointed to a decrease of pathology in IS birds. Since dexamethasone mostly affects heterophils, the study suggests that these cells play a role in the development of lesions associated with chronic fowl cholera in chickens.

Stinging nettle and neem enhance antibody response to local killed and imported live infectious bursal disease vaccines in indigenous chicken in Kenya

Abstract Immune responses are critical for protection of chickens from infectious bursal disease (IBD). In this study, the antibody response‐enhancing effect of drinking water supplementation of 1% stinging nettle and neem on different IBD vaccines and vaccination regimes was evaluated, using 36 (n = 36) specific antibody negative indigenous chicks. The birds were allocated into 3 groups as follows: 1A‐C, 2A‐C, and 3A‐B, while group 3C acted as the unvaccinated non‐supplemented control. A local inactivated K1 and imported live attenuated D78 IBD vaccines were given to groups 1A‐C and 3A‐B at 14 and 28 d of age, respectively. A combination of K1 and D78 vaccines was given 30 d apart to groups 2A and 2B (D78 at 14 and 21 d and K1 at 44 d of age) and on the same d to group 2C at 14 and 28 d of age. Stinging nettle was given in water to groups 1B, 2B, and 2C, and neem to groups 1C, 2A, and 3B. Birds were bled weekly and immune responses monitored using indirect ELISA. Both neem and stinging nettle had antibody response‐enhancing effects in groups 1B and 1C, receiving the local inactivated K1 vaccine. There were significant differences (P < 0.05) in antibody titers between groups 1A and 2C. Stinging nettle induced earlier onset of high antibody responses in group 2C and persistent titers (>3.8 log10) from the third week in group 2B. Imported live D78 vaccine induced higher antibody titers compared to the local inactivated K1 vaccine. Groups 2B and 2C receiving a combination of the local K1 and imported live attenuated D78 vaccines had the highest antibody titers. Adoption of stinging nettle supplementation and a prime‐boost program involving use of a local virus isolates‐derived vaccine is recommended.

Isolation of Infectious Bursal Disease Virus Using Indigenous Chicken Embryos in Kenya.

Infectious bursal disease virus (IBDV) isolates were recovered from outbreaks to initiate activities towards developing a local vaccine strain. Use of indigenous chicken embryos was exploited to determine their potential, promote utilization of local resources for research, and enhance household economic activities. Bursa of Fabricius (BFs) samples from outbreaks shown to be IBDV positive was homogenized and inoculated in 4-week-old specific pathogen-free (SPF) IBDV seronegative white leghorn chicks. The harvested virus was inoculated into 11-day-old indigenous chicken embryos that were IBDV seronegative and passaged serially three times after which they were inoculated into 4-week-old indigenous chicks to test for presence and virulence of propagated virus. Out of 153 BFs collected from outbreaks, 43.8% (67/153) were positive for IBDV antigen and 65.7% (44/67) caused disease in SPF chicks. The embryo mean mortalities were 88% on primary inoculation, 94% in 1st passage, 91% in 2nd passage, and 67% in 3rd passage. After the third passage in embryos all the 44 isolates were virulent in 4-week-old indigenous chicks. The results show that indigenous chicken embryos support growth of IBDV and can be used to propagate the virus as an alternative viral propagating tool for respective vaccine preparation.

Newcastle disease virus and antibody levels in matched sera, ovules and mature eggs of indigenous village hens

In this study, one hundred and thirty three non - vaccinated village hens in lay were tested for carriage of Newcastle disease virus and presence of antibody against the virus in sera, ovules and eggs. Blood was obtained from the hens through wing venipuncture while matched ovules and mature eggs were taken from the oviducts. Cloacal and oropharyngeal swabs were collected from each hen for virus isolation. Haemagglutination inhibition assay was performed for all sera and egg yolk samples. Protective serum antibody titres of ≥3 (log2) were recorded in 5.3% of the naturally exposed, indigenous village hens. Antibody titers to Newcastle disease virus in the yolks were higher than in their sera (230.08 ± 40.05; 1.56 ± 0.74 for egg yolk and sera, respectively) (P Keywords: Newcastle disease, egg yolk, nonvaccinated, village chickens