P G Mbuthia

Specific Detection of Pasteurella multocida in Chickens with Fowl Cholera and in Pig Lung Tissues Using Fluorescent rRNA In Situ Hybridization

ABSTRACT A Pasteurella multocida species-specific oligonucleotide probe, pmhyb449, targeting 16S rRNA was designed and evaluated by whole-cell hybridization against 22 selected reference strains in animal tissues. It differentiated P. multocida from other bacterial species of the familiesPasteurellaceae and Enterobacteriaceaeand also from divergent species of the orderCytophagales (except biovar 2 strains ofPasteurella avium and Pasteurella canis,which have high 16S rRNA similarity to P. multocida). The potential of the probe for specific identification and differentiation of P. multocida was further detected in formalin-fixed paraffin-embedded lung tissues from experimental fowl cholera in chickens and infections in pigs. In chicken lung tissuesP. multocida cells were detected singly, in pairs, as microcolonies, and as massive colonies within air capillaries (septa and lumen), parabronchial septa, and blood vessels (wall and lumen). In pig lung, postmortem-injected P. multocida was detected in the alveoli (lumen and wall), and in both animals the bacterial cells were seen in the bronchi. The results showed that with the oligonucleotide probe pmhyb449, fluorescent in situ hybridization is a suitable and fast method for specific detection of P. multocida in histological formalin-fixed tissues. The test was replicable and reproducible and is recommended as a supplementary test for diagnosis and as a tool in pathogenesis studies of fowl cholera and respiratory tract infections in pigs due to P. multocida.

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.

Natural besnoitiosis in a rabbit

An adult female rabbit was submitted for necropsy after sudden death. Pneumonia and nephritis were diagnosed by gross examination. On histological examination. Besnoitia cysts were seen in the pulmonary interalveolar tissue. The Besnoitia cysts were morphologically normal in appearance, measured 127 to 185 microns in diameter and provoked mild mononuclear inflammatory reaction. To the best of our knowledge there has been no previous report of natural besnoitiosis in rabbits.

Prevalence of gastrointestinal helminths and management practices for dogs in the Greater Accra region of Ghana

Toxocariosis and ancylostomosis remain the most important parasitic infections affecting companion animals worldwide and pose a risk to animal and human health. Information on these infections in dogs in Ghana is inadequate. A cross sectional study was undertaken to determine the occurrence of gastrointestinal helminths infections and management practices of dogs in the Greater Accra Region (GAR) of Ghana. Faecal samples were obtained from 380 dogs from communities in 11 out of 16 districts in the GAR. Coprological examination of the samples was performed using the modified McMaster technique. Management practices for control of helminths in dogs were assessed through questionnaire interviews of the dog owners. Most dogs (70.7%) were kept for security reasons and were not housed (61.8%). Prevalence of gastrointestinal helminths was 62.6%. Hookworm eggs were found in 178 (46.8%) dogs, Toxocara canis eggs in 22 (5.8%) and mixed infections of hookworms and T. canis in 38 (10.0%). Dipylidium caninum was found in 51 (13.4%) dogs, while Isospora species was in 33 (8.5%) dogs. Most households (68%; 133/194) of the sampled dogs had at least a child below the age of 5 years. Hookworm, T. canis and D. caninum were the zoonotic gastrointestinal helminths prevalent in dogs in the study area. Lack of housing for dogs creates ideal conditions for infection and spread of the zoonotic parasites.

Generalised demodicosis in a Friesian heifer from a zero-grazing unit

A Friesian heifer with generalised skin lesions was slaughtered after unsuccessful treatment. It had thickened skin with lumps and nodules, with the severely affected parts thrown into folds over the eyelids, ears, most of the head, neck, legs and perineal area. The affected skin was soft and squamous in appearance. On postmortem examination, all the skin layers were affected and were 10-22 mm thick. There was also lymphadenopathy. Histological examination showed the presence of dermatitis characterised by follicular inflammation. Multiple follicular cysts with keratin squames and numerous demodectic mites were seen. Some mites had migrated to the peripheral lymph nodes causing eosinophilic lymphadenitis and panniculitis of the subcutis.

Risk factors associated with infectious bursal disease vaccination failures in broiler farms in Kenya.

Immunization together with application of biosecurity measures are the principal methods of preventing infectious bursal disease outbreaks in high-risk areas. However, outbreaks in vaccinated chicken flocks have been reported in many parts of the world as a result of factors of vaccine virus, animal, or vaccine handler. In Kenya, such outbreaks have been reported, but the causes have not been studied. This study aimed at determining the risk factors associated with vaccine handling leading to vaccine failure in broiler flocks in Kwale County, Kenya. Structured questionnaires and visual observations were used to collect data from 83 broiler farms, 6 breeding farms, and 17 vaccine outlets. Relative risk (RR) analysis was used to determine the association between identified potential risk factors and vaccination failure. Results show that vaccines were properly handled in all vaccine outlet shops. Breeding farms maintained high levels of biosecurity and employed standard vaccine handling practices. Basic biosecurity practices were poor in broiler farms. Broiler farms failed to meet all the recommended standard procedures for vaccine storage, reconstitution, and administration. Risk factors included poor vaccine storage (RR = 8.7) and use of few drinkers to administer vaccine (RR = 5.8); traces of disinfectants in drinkers used to administer live vaccine (RR = 2.8); use of wrong vaccine—infectious bronchitis instead of infectious bursal disease vaccine (RR = 2.1); and use of improper diluents (RR = 1.6). Broiler farmers need training on basic farm biosecurity measures and standard vaccine handling practices.

Detection and Prevention of Highly Pathogenic Avian Influenza in Communities with High Poultry Disease Burdens

Abstract The implementation of strategies to detect, prevent, and control highly pathogenic avian influenza (HPAI) in developing countries presents several challenges, one of which is the presence of other diseases in poultry populations. Training workshops in developing countries using the Avian Flu School have revealed that in areas with heavy Newcastle disease burdens, smallholder poultry keepers do not recognize HPAI as an immediate threat. We have developed a strategy to address the more proximal needs and priorities of communities with free-ranging poultry flocks as a means to create value in poultry, and thus to improve disease detection and prevention overall. To this end, we have created the Poultry Health and Well-Being for Development project, which trains graduate veterinarians and paraprofessionals in poultry disease diagnosis, control, and treatment. These trainees then serve their local communities to improve poultry health and to implement disease detection and management programs.

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.