First detection and isolation of infectious haematopoietic necrosis virus from farmed rainbow trout in Nyeri County, Kenya.

Infectious haematopoietic necrosis virus (IHNV) is the causative agent of infectious haematopoietic necrosis, a disease of salmonid responsible for great economic losses. The disease occurs in most parts of the world where rainbow trout is reared but has not been previously reported in Kenya. In this study, rainbow trout fry and growers from two farms in Nyeri County were screened for IHNV. Whole fry (n = 4 from each farm) and kidney samples from growers (n = 15 and n = 6 from the two farms, respectively) were collected and preserved for cell culture examination or PCR analysis. Screening of samples was done by PCR followed by sequencing of the glycoprotein gene of the virus. Demonstration of the virus was done by propagation in EPC cells followed by the indirect fluorescence antibody test (IFAT). The results revealed the presence of IHNV at low prevalence of 0.1 and 0.4 for the two farms. The virus was confirmed both by IFAT and by partial sequencing of the G gene. Phylogenetic analysis revealed that the Kenyan isolates were identical to those of the J genogroup found mostly in Asia. The findings have implications for biosecurity measures and import regulations for the Kenyan rainbow trout industry.

Antimicrobial Usage, Susceptibility Profiles, and Resistance Genes in Campylobacter Isolated from Cattle, Chicken, and Water Samples in Kajiado County, Kenya.

Campylobacter organisms are the major cause of bacterial gastroenteritis and diarrhoeal illness in man and livestock. Campylobacter is growingly becoming resistant to critically crucial antibiotics; thereby presenting public health challenge. This study aimed at establishing antimicrobial use, susceptibility profiles, and resistance genes in Campylobacter isolates recovered from chicken, cattle, and cattle-trough water samples. The study was conducted between October 2020 and May 2022 and involved the revival of cryopreserved Campylobacter isolates confirmed by PCR from a previous prevalence study in Kajiado County, Kenya. Data on antimicrobial use and animal health-seeking behaviour among livestock owners (from the same farms where sampling was done for the prevalence study) were collected through interview using a pretested semistructured questionnaire. One hundred and three isolates (29 C. coli (16 cattle isolates, 9 chicken isolates, and 4 water isolates) and 74 C. jejuni (38 cattle isolates, 30 chicken isolates, and 6 water isolates)) were assayed for phenotypic antibiotic susceptibility profile using the Kirby-Bauer disk diffusion method for ampicillin (AX), tetracycline (TE), gentamicin (GEN), erythromycin (E), ciprofloxacin (CIP), and nalidixic acid (NA). Furthermore, detection of genes conferring resistance to tetracyclines (tet (O), ß-lactams (bla OXA-61), aminoglycosides (aph-3-1), (fluoro)quinolones (gyrA), and multidrug efflux pump (cmeB) encoding resistance to multiple antibiotics was detected by mPCR and confirmed by DNA sequencing. The correlation between antibiotic use and resistance phenotypes was determined using the Pearson's correlation coefficient (r) method. Tetracyclines, aminoglycosides, and ß-lactam-based antibiotics were the most commonly used antimicrobials; with most farms generally reported using antimicrobials in chicken production systems than in cattle. The highest resistance amongst isolates was recorded in ampicillin (100%), followed by tetracycline (97.1%), erythromycin (75.7%), and ciprofloxacin (63.1%). Multidrug resistance (MDR) profile was observed in 99 of 103 (96.1%) isolates; with all the Campylobacter coli isolates displaying MDR. All chicken isolates (39/39, 100%) exhibited multidrug resistance. The AX-TE-E-CIP was the most common MDR pattern at 29.1%. The antibiotic resistance genes were detected as follows: tet (O), gyrA, cmeB, bla OXA-61 , and aph-3-1 genes were detected at 93.2%, 61.2%, 54.4%, 36.9%, and 22.3% of all Campylobacter isolates, respectively. The highest correlations were found between tet (O) and tetracycline-resistant phenotypes for C. coli (96.4%) and C. jejuni (95.8%). A moderate level of concordance was observed between the Kirby-Bauer disk diffusion method (phenotypic assay) and PCR (genotypic assay) for tetracycline in both C. coli (kappa coefficient = 0.65) and C. jejuni (kappa coefficient = 0.55). The study discloses relatively high resistance profiles and multidrug resistance to antibiotics of critical importance in humans. The evolution of the multidrug-resistantCampylobacter isolates has been linked to the use and misuse of antimicrobials. This poses a potential hazard to public and animal health, necessitating need to reduce the use of antibiotics in livestock husbandry practice coupled with stringent biosecurity measures to mitigate antimicrobial resistance.

Seasonal Prevalence and Molecular Identification of Thermophilic Campylobacter from Chicken, Cattle, and Respective Drinking Water in Kajiado County, Kenya.

Thermophilic Campylobacter species are a leading cause of human gastroenteritis throughout the world and have been implicated in reproductive disorders (abortion), mastitis, enteritis, and/or diarrhoea in livestock. A cross-sectional survey was conducted in Kajiado County to determine prevalence, seasonality, and molecular detection of thermophilic Campylobacter species (with emphasis on C. jejuni, C. coli, and other thermophilic Campylobacter species) in chicken, cattle, and respective pooled drinking water. A total of 457 samples comprising 265 cattle rectal swabs, 142 chicken cloacal swabs, and 50 trough water samples were collected from 55 randomly selected smallholder farms. Individual samples were subjected to standard techniques for isolation and biochemical tests, followed by singleplex polymerase chain reaction (sPCR) assays for identification and confirmation of genus and species. Overall, thermophilic Campylobacter prevalence was 35.4% (95% confidence interval (95% CI) = 31.0-39.8), with C. jejuni dominating at 55.6% (95% CI = 47.9-63.3%) over C. coli in all sample types. The highest thermophilic Campylobacter prevalence was observed in cloacal swabs of live chicken at 44.4% (95% CI = 36.2-52.6%), followed by rectal swabs from live cattle at 30.9% (95% CI = 25.3-36.5%). Water samples from cattle drinkers/trough were found to be contaminated at 34% (95% CI = 20.9-47.1%). The isolation rate was higher in cattle under the confinement system (44.3%) (95% CI = 36.1-52.5%) than in those under the free-roaming grazing system. Thermophilic Campylobacter species were isolated in both seasons, with higher prevalence (39.8% (95% CI = 33.6-45.9)) recorded during rainy and cold season in all sample types except for water. There was significant (P < 0.05) association between season and thermophilic Campylobacter occurrence, even though there were no statistical differences in the prevalence values across the two seasons. Results of this study demonstrate that cattle, chicken, and respective drinking water harbour potentially pathogenic thermophilic campylobacters, with C. jejuni being widely distributed among farms. It is possible that seasonal variations and cattle confinement result in differences in thermophilic Campylobacter carriage. Further epidemiological and phylogenetic studies comparing distribution of thermophilic Campylobacter spp. isolates in livestock, environmental, and human samples are recommended to establish source attribution to reduce the impact of resultant diseases for the wellbeing of public and livestock.

Gross and Histopathology of Goats Feeding on Opuntia stricta in Laikipia County, Kenya.

Various plant species such as Opuntia stricta have developed defensive measures, namely, spines, thorns, and other sharp pointed structures to protect themselves from herbivores and other animals feeding on them. Opuntia stricta has invaded the northern part of Laikipia County, Kenya, and its fruits are protected by small spines called glochids. This study determined the pathology in goats feeding on this plant in Laikipia County. Eighteen goats that had eaten the plant and six others that were raised in a ranch without O. stricta were purchased for the study. All study animals were clinically examined for lesions and euthanized for necropsy examination. Clinically, goats affected by O. stricta had poor body condition, wounds on various body parts, and diarrhea. Variable numbers of O. stricta spines occurred externally on the skin throughout the body and elicited pain, swelling, and ulcerative wounds on affected parts. Internal lesions were observed in subcutaneous tissues (100%), together with stomatitis, cheilitis, gingivitis, glossitis, abomasitis (100%), rumen, reticulum, omasum thinning and loss of papillae (72.2%), esophagitis, and duodenitis (5.6%). Carcasses had gelatinous fat and muscular atrophy. Other gross lesions were generalized viscera atrophy, edema, subcutaneous emphysema, lymphadenopathy, abscesses, ascites, hydrothorax, and hydropericardium. The abomasum wall and its mucosal folds were swollen with edema, haemorrhages, and scattered foci of abscesses. Histopathology confirmed the main lesions in all affected goats were foreign-body granulomas which were located in all organs with gross lesions. Goats from O. stricta-free ranches had no spines or lesions. The pathological effects caused by O. stricta resulted in emaciated goats due to pain, inability to masticate and assimilate food, and stress, resulting in poor carcass and organs quality and possible condemnation and death. This could affect the socioeconomics and livelihoods of communities in the study area, and therefore, the spread of this plant needs to be controlled.

Management Practices, Farmers' Knowledge of Diseased Fish, and Their Occurrence in Fish Farms in Nyeri County, Kenya.

In this study, fish farmers' management practices, occurrence, and knowledge of fish diseases in Nyeri County, Kenya, were evaluated. Fish farming management practices for small-scale farmers in Kenya have numerous challenges which have led to disease occurrence and reduced production. Moreover, the impact and association of these challenges to farmers' knowledge of fish diseases and their burden has not been fully studied. A semistructured questionnaire was used to capture farmers' biodata, fish species farmed, and farmers' management practices such as handling of nets, pond fertilization, and disposal of fish waste. Farmers' knowledge of fish diseases was based on their ability to identify independent and dependent variable indicators. Independent variables included clinical signs, decreased feeding, bulging eyes, floating on water, abdominal swelling, bulging eyes, abnormal skin color, reduced growth, and abnormal swimming with fish death as were the dependent variable. A total of 208 farmers were interviewed and included those of tilapia (134), mixed tilapia and catfish (40), catfish (22), rainbow trout, and five dams under cooperative management. Tilapia was the most kept fish species (66.8%) followed by polyculture of tilapia and catfish (20%) and rainbow trout (2%). Most respondents were male (78.5%) over 51 years of age (50%). Fifty percent of the respondents had secondary school education. There was a significant association between deaths and sharing of nets in Kieni East subcounty (p=0.0049, chi-square), while on-farm fish waste disposing appeared to cause higher deaths compared to burning of the waste although not statistically significant (p=0.13). Few respondents observed decreased feed uptake (<20%) and poor growth. Fifty-seven percent of farmers reported mortalities. Fish poor growth, floating in water, and management practices in subcounties had significant effect on fish deaths. The farmers had knowledge of signs of diseased fish, but there was paucity of knowing the specific causes of disease. Farmers need to be empowered on best aquaculture husbandry to avoid disease transmission and specific fish disease signs to enhance proper reporting of disease for subsequent mitigation measures.

Causes of calf mortality in peri-urban area of Nairobi, Kenya.

The study reported data from 507 post-mortem records in the Department of Pathology, Microbiology and Parasitology, Faculty of Veterinary Medicine, University of Nairobi, Kenya. The records were from carcasses obtained from the peri-urban area of Nairobi during a 20-year period between 1990 and 2009. Approximately 80% (393/507) of the calf carcasses had their diagnosis made through post-mortem examination, while the rest (114/507) were inconclusive. Just less than half (48.3%) of the calf carcasses presented had their age specified by the owners compared to 51.7% whose age was not specified. For calf carcasses whose age was specified by the owners, those indicated as more than 3 months were one-and-a-half times as many as those below 3 months old. The proportion of female carcasses (53.8%, 273/507) presented for post-mortem were slightly higher than the male carcasses (46.2%, 234/507). Diseases or conditions of the respiratory system were the most common 17.7% (97/507) while gastrointestinal tract (GIT) was second and affected 16.1% (88/507) of the cases. Another small number, 3.3% (18/507), died from bloat giving the total cases associated with GIT as 19.4% (106/507). Severe calf malnutrition and septicaemia were the third most reported causes of calf mortality in similar proportions at 14.3% (78/507) and 14.4% (79/507), respectively. Other minor causes of calf mortality were tick-borne diseases 8.6% (47/507), helminthiasis and poisoning, 2.9% (16/507) and 1.8% (10/507), respectively.

Haemato-biochemical changes and prevalence of parasitic infections of indigenous chicken sold in markets of Kiambu County, Kenya.

This study aimed at determining parasitic prevalence and probable haemato-biochemical changes that may occur from parasitic infections in marketed indigenous chickens in Kiambu County, Kenya. Thirty adult chickens were purchased and examined for ectoparasites, haemoparasites and haemato-biochemical changes. Post mortem was conducted to recover gastro-intestinal parasites and fecal samples taken for egg/oocyst counts. Forty-seven percent (14/30) of chickens examined were in poor body condition, 43% (13/30) in fair and 10% (3/30) in good body condition. Ectoparasites infection prevalence was 66.7% (20/30). Four haemoparasites were isolated. Overall helminths prevalence was 86.6% (26/30), nematodes at 76.7% (23/30) and cestodes at 40% (12/30). After processing fecal samples, 30% (9/30) were positive for helminth eggs and 30% (9/30) had coccidial oocysts. Relative to normal values, total erythrocyte count was low and total leucocyte count with band cells high. Mean haematocrit and heterophil values were high (p=0.0005; p=0.0061). Mean lymphocyte count was low (p=0.0128) in chickens with ectoparasitic infestation. Eosinophils increased significantly (p=0.0363) although mean erythrocytes counts decreased (p=0.0176), in chickens with gastrointestinal parasites. Creatine phosphokinase and blood glucose levels were high, serum protein and albumin levels were low. Blood glucose level decreased significantly (p=0.0239) and total plasma protein increased (p=0.045) in chickens with Haemoproteus spp. infection. The study showed, ecto- and endo-parasites are prevalent and may contribute to alteration of haemato-biochemical parameters of sub-clinically infected marketed indigenous chickens. These results are expected to contribute towards and encourage usage of clinico-pathological parameter testing as a measure of poultry health status for enhanced poultry disease diagnoses.

Antibiotic and Disinfectant Susceptibility Patterns of Bacteria Isolated from Farmed Fish in Kirinyaga County, Kenya.

Fish bacterial pathogens cause diseases which result in a considerable economic impact on the aquaculture industry, necessitating the use of antimicrobials for their control. However, intensive and indiscriminate use of antimicrobials has led to increased occurrence of drug resistance in pathogenic bacteria, as well as normal flora. The aim of the current study was to determine the susceptibility patterns of bacteria isolated from fish, with respect to some commonly used antibiotics and disinfectants. Bacteria were isolated between December 2017 and April 2018 from farmed Nile tilapia, African catfish, goldfish, and koi carp in Kirinyaga County, Kenya. Antibiotic and disinfectant susceptibility patterns of 48 isolates belonging to the genera Aeromonas, Proteus, Klebsiella, Citrobacter, Salmonella, Streptococcus, Pseudomonas, Escherichia, Serratia, and Micrococcus were established using the Kirby-Bauer disc diffusion method and agar well diffusion technique, respectively. The antibiotics evaluated included ampicillin, tetracycline, co-trimoxazole, streptomycin, kanamycin, gentamicin, co-trimoxazole, and chloramphenicol, while the disinfectants tested were quaternary ammonium compound, formalin, hydrogen peroxide, sodium hypochlorite, and iodine. All the bacteria except Micrococcus, Escherichia, and Salmonella species showed multiple drug resistance patterns. Streptococcus showed resistance to six antibiotics, while Proteus, Pseudomonas, and Serratia were resistant to five antibiotics. The multiple antibiotic resistance index ranged from 0.1 to 0.8, with Streptococcus spp. having the highest score value. All the organisms were sensitive to gentamicin, while co-trimoxazole and ampicillin showed the highest resistance at 73% (n = 34) and 62% (n = 31), respectively. Most of the disinfectants showed antibacterial activity with varying magnitudes. The isolates were 100% sensitive to hydrogen peroxide and formalin, but were resistant to sodium hypochlorite at recommended user-dilution. The study has shown that some of the bacterial isolates were resistant to common antibiotics and disinfectants; thus, it is recommended to include an antibiogram whenever making any therapeutic decision. The resistant bacteria may transmit resistance genes to other fish bacteria and also to human bacteria, thus making it difficult to treat the resultant disease(s); thus, there is a possibility that these resistant bacteria may be transmitted to humans who consume or handle the carrier fish. It is, therefore, advisable that fish are cooked properly before consumption, so as to kill bacteria that may be present.

Natural Concurrent Infections with Black Spot Disease and Multiple Bacteriosis in Farmed Nile Tilapia in Central Kenya.

Nile tilapia (Oreochromis niloticus) is the most cultured and available fish for Kenyan consumers, and therefore, any tilapine disease deprives them the valuable source of protein. Nile tilapia farm was diagnosed with severe concurrent black spot disease and multiple bacteriosis using gross lesions and parasitological, histopathology, and standard bacteriological procedures. A total of 25 fish were sampled and inspected, and all of them had raised, macroscopic 1 mm-sized black spot lesions. The mean intensity of black spots per fish was 728 with an abundance of 2-1740 metacercariae cysts per fish. A high intensity of black spot infestation was observed in the fins (43.9%), skin and underlying muscles (18.3%), and gills (18%). In addition, histopathological data confirmed presence of a metacercaria of Neascus spp. as the aetiological agent of black spot disease. Furthermore, a thick fibrous capsule around the metacercaria, black pigment melanomacrophages, and moderate muscle atrophy were observed. The most prevalent bacteria isolated were Aeromonas, Enterobacter cloacae, Klebsiella pneumoniae, and Micrococcus luteus. Physicochemical parameters of pond water were temperature (28.2°C), dissolved oxygen (4.2 mgl-1), pH (8.5), ammonia free nitrogen (15.8 mgl-1), alkalinity (112 mgl-1), hardness (68 mgl-1), nitrites (0.058 mgl-1), nitrates (58 mgl-1), and phosphates (0.046 mgl-1). However, the levels of nitrates, nitrites, alkalinity, and ammonia free nitrogen exceeded the recommended limits. In conclusion, these findings suggest that coinfections by these organisms coupled by water quality-related stress can be associated with low-grade mortality observed in postfingerling tilapia as well as reduced growth. The authors recommended immediate destocking, thorough disinfection, and control of piscivorous birds. Moreover, attention ought to be geared towards prevention of parasitic infestations in fish so as to minimize fish deaths related to secondary bacteriosis. Further experimental studies should be carried out to elucidate the relationship of these pathogens.

Fish Husbandry Practices and Water Quality in Central Kenya: Potential Risk Factors for Fish Mortality and Infectious Diseases.

Fish mortality has an enormous impact on the aquaculture industry by reducing fish production and slowing industrial growth. A cross-sectional study was carried out in Kirinyaga County, Central Kenya, to evaluate potential risks of fish mortality and disease transmission and suitability of pond water for rearing fish. A semistructured questionnaire that focused on general information, management practices, and disease history was administered to 92 small-scale fish farmers. Parasitological examination of fish sampled from selected farms (farms that were reporting mortality at the time of sampling) was done by following the standard procedure. Water quality parameters for 33 ponds were evaluated in situ (recorded on pond site) and ex situ (analysed at the laboratory) following the standard methods. The risks were assessed by adjusted odds ratio based on univariate regression analysis. Prevalent fish husbandry practices that were found to be associated with fish mortality and acquisition of pathogens in the study area were the use of raw livestock manure (0R = 1.500), high fish stocking density (0R = 1.168), and feeding fish on homemade rations (0R = 1.128). Parasitological investigation found infestation with Diplostomum spp., Dactylogyrus spp., Clinostomum spp., and Piscicola leeches. Water temperature and pH were found fit for rearing fish. Of the 33 fishpond water samples tested, 1 (3%) and 6 (18%) exceeded the recommended limits of <100 mg/L and <0.2 mg/L of nitrate and nitrite, respectively. Of the 29 fishpond water tested, 15 (59%) exceeded the recommended limits of <100 mg/L of total ammonia. The findings show that the use of raw livestock manure, high fish stocking density, high nitrates and nitrites, and high ammonia levels in fishponds are potential risk factors for fish mortality and acquisition of infectious pathogens in a pond environment in a rural setup, in Central Kenya. There is a need to address the above factors in small-scale farming practices to minimize fish loss and also to prevent the occurrence and spread of infectious pathogens.

A systematic review of analgesia practices in dogs undergoing ovariohysterectomy.

AIM: This was a systematic review conducted to evaluate the analgesic drugs and techniques used in the management of pain in dogs undergoing ovariohysterectomy. MATERIALS AND METHODS: Systematic searches in PubMed, Google Scholar, and ScienceDirect were conducted for peer-reviewed articles written in English and published from 1995 to 2015. The key search words were dogs, ovariohysterectomy, pain, and analgesics. This was followed by a manual search of the references within the primary data sources. Inclusion and exclusion of studies and data extraction were performed independently by two reviewers. All randomized studies evaluating the effects of analgesics during ovariohysterectomy in dogs were included. RESULTS: A total of 31 trials met the criteria and were, therefore, included in the study. Data on the type of analgesic drugs used, the technique of administration, and the need for rescue analgesia were extracted from the papers. Individual analgesic protocols were used in 83.9% of the studies compared to multimodal drug therapy, which was used in 16.1% of the studies. Opioids were used in 39.0% of studies, nonsteroidal anti-inflammatory drugs (NSAIDs) in 19.4%, a combination of NSAIDs and opioids in 19.4%, local analgesics in 6.5%, and acupuncture in 3.2% of the studies. Drug administration was done using three approaches that included pre-operative (64.5%), post-operative (22.6%) as well as combined pre- and post-operative approach (12.9%). In 77.4% of the studies, administration of analgesics was done once, while in 12.9%, it was done as a 72-h post-operative course. 24-h and 48-h courses of post-operative pain therapy were done in 6.5% and 3.2% of the studies, respectively. About 57% of the dogs in the control groups required rescue analgesia as compared to 21.6% in the single and 11.3% in multimodal drug therapy groups. The requirement for rescue analgesics was highest in dogs treated using acupuncture (43.8%) and lowest in dogs treated using NSAID-opioid combination (8.6%). Fewer dogs among those that received pain medication preoperatively and postoperatively required rescue analgesia compared to those in groups given drugs before and after surgery only. More dogs (26.4%) among those given analgesics only once postoperatively required rescue analgesia as compared to those that received analgesics daily for 72 h (4.4%). CONCLUSIONS: This study provides evidence that opioids are the mainstream analgesic drugs used in managing acute post-operative pain in dogs' post-ovariohysterectomy. In addition, multimodal drug therapy, particularly, NSAID-opioids combination is more effective for pain management than single drug administration. Administering analgesics both before and after surgery is associated with better outcomes and so is a protracted course of post-operative pain therapy. Although these practices should be encouraged, controlled studies should be conducted to conclusively determine the best practices for pain management in dogs undergoing ovariohysterectomy.

Myiasis in Dogs in the Greater Accra Region of Ghana.

Myiasis is the infestation of tissues of live vertebrate animals and humans with dipterous larvae. In sub-Saharan Africa, Cordylobia anthropohaga and Cordylobia rodhaini are known to be responsible for cutaneous myiasis in animals and humans. Human cases of myiasis, purportedly acquired in Ghana but diagnosed in other countries, have been reported; however, published data on its occurrence in animals in Ghana is unavailable. This study assessed the prevalence of canine myiasis among owned dogs in the Greater Accra region (GAR) of Ghana. A cross-sectional study was conducted in the Greater Accra region of Ghana, selected for being the region with the highest estimated population density of owned dogs. Physical examination and demographic characteristics of the study dogs were assessed. Management of the dogs was assessed through a questionnaire administered to the dog owners. A total of 392 owned dogs were sampled. Twenty-nine (7.4%) had cutaneous myiasis caused by C. rodhaini. In addition, one (0.2%) of the dogs had intestinal myiasis, with Dermatobia hominis as the offending larvae. Among the breeds of dogs with myiasis, the mongrel was most affected, with 24 (82.8%) out of the 29 cases. The mongrels, majority of which (24; 82.8%) were males, were left to roam freely in the community. Results from this study demonstrate that C. rodhaini and D. hominis are important causes of myiasis in owned dogs in the GAR of Ghana. Dogs could play a role in the spread of myiasis to humans, with its attendant public health implications.

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.