Detection of antibodies against Ornithodoros moubata salivary antigens and their association with detection of African swine fever virus in pigs slaughtered in central Uganda.

Introduction: African swine fever (ASF) is an important disease of pigs in sub-Saharan Africa and Uganda and is threatening the pig population and agricultural economy of other continents. ASF virus (ASFV) can be transmitted from wild suids to domestic pigs through soft ticks of the Ornithodoros species. The aim of this study was to understand the relationship between domestic pigs' O. moubata tick exposure and ASFV status. Methods: Pigs were sampled from six abattoirs in the Kampala metropolitan area of Uganda from May 2021 through June 2022. Blood, serum, and tissue samples were collected. Serum was tested for antibodies against the rtTSGP1 salivary antigens of O. moubata ticks using an indirect ELISA assay. Blood and tissue samples from pigs were tested to detect ASFV using qPCR. Probability of tick exposure was categorized based on sample-to-positive ratio cut-off points. Results: Out of 1,328 serum samples tested, there were 828 (62.3%) samples with a negligible probability; 369 (27.8%) with a medium probability; 90 (6.8%) with a high probability, and 41 (3.1%) with a very high probability of exposure to the O. moubata salivary antigen. There was a statistically significant association between the pigs' O. moubata exposure and ASFV status with a higher proportion of pigs having a very high probability of infection if they were ASFV positive by blood, tonsil, and lymph nodes. Discussion: These results suggested that tick exposure was associated with ASFV transmission in Uganda. There were ASFV qPCR positive pigs that had no O. moubata exposure as well, which highlights that pig-to-pig and indirect contact transmission still play a significant role. This work highlights the need for further work in Uganda to investigate these transmission factors related to the O. moubata tick and ASFV transmission.

Reflections on Drivers for the Emergence and Spread of Antimicrobial Resistant Bacteria Detected from Chickens reared on Commercial Layer Farms in Mukono District, Uganda.

Purpose: We investigated the fecal carriage of antimicrobial resistant Escherichia coli and potential practices influencing antimicrobial resistance (AMR) dynamics among poultry farm settings in Mukono District, Uganda. Methods: Twenty-nine commercial layer farms were visited and samples collected from 10 birds. The samples were then subjected to culture and sensitivity testing. The investigative framework for antimicrobial stewardship practices (IFAP) was used as a participatory tool to generate data through interviews and observations on antimicrobial use, drivers for use, players, and actions following non-responsive treatment outcomes. Results: The cultures done on 290 cloacal swabs yielded a total of 273 Escherichia coli isolates (94.1% recovery rate) which were tested in vitro for their sensitivity to different antibiotics. The prevalence of multi-drug resistant E. coli was 59.3% (162/273). A high prevalence of resistance to tetracycline (91.6%, n = 250) and trimethoprim sulphamethoxazole (70.3%, n = 192) was noted. In this collection of isolates, the prevalence of molecular determinants associated with the predominant phenotypes was; tetA (79.3%; 138/174), tetB (17.2%; 30/174), tetC (7.5%; 13/174), sul1 (11.5%; 20/174), and sul2 (60.3%; 105/174). Responses derived using the IFAP revealed several vices related to misuse and overuse of antibiotics, a threat to the poultry industry. The farmers also reported habits of selling off sick birds for slaughter when treatment outcomes were non-responsive. Such a practice could drive dissemination of antimicrobial resistant organisms and antibiotic residues to the consumers of those poultry products. Conclusion: The IFAP tool was useful and can be modified, and adopted for use in engaging agricultural communities in participatory AMR surveillance. A high carriage of multi-drug resistant E. coli was detected in the birds. On these farms, the worrying antimicrobial stewardship practices discovered could be sponsoring the emergence and spread of antimicrobial resistant bacteria in the Ugandan context.

Spatiotemporal description of African swine fever virus nucleic acid and antibodies detected in pigs sampled at abattoirs in the greater Kampala metropolitan area, Uganda from May 2021 through June 2022.

BACKGROUND: African swine fever virus (ASFV) infections in Africa cause hemorrhagic disease in domestic pigs and is maintained by a sylvatic cycle in warthogs. It is endemic in Uganda, leading to significant economic losses. Previous studies performed in rural areas and in Kampala had differing diagnostic results. The purpose of this study was to provide a robust spatial, temporal, and diagnostic summary of pigs slaughtered in the greater Kampala metropolitan area over the course of one year. This study characterized 1208 to 1323 serum, blood, and tissue samples collected from pigs at six abattoirs in the greater Kampala metropolitan area of Uganda monthly from May 2021 through June 2022. Validated and standardized serologic and molecular diagnostics were used. RESULTS: Only 0.15% of pigs had detectable antibodies against ASFV, suggesting low survival rates or pre-clinical diagnosis. Yet, 59.5% of pigs were positive for ASFV DNA. Blood had the lowest detection rate (15.3%) while tonsil and lymph nodes had the highest (38% and 37.5%, respectively), spleen samples (31.5%) were in between. Agreement between sample types was fair to moderate overall. A significant seasonality of ASFV infections emerged with infections found predominately in the dry seasons. Spatial assessments revealed that the greater Kampala metropolitan area abattoirs have a catchment area that overlaps with Uganda's most pig dense regions. CONCLUSIONS: Pigs at greater Kampala metropolitan area abattoirs can be sentinels for acute disease throughout the pig dense region of Uganda, particularly in the dry seasons. The high prevalence detected suggests that pigs are sold in response to local reports of ASFV infections (panic sales). Serological surveillance is not useful, as very few pigs seroconverted in this study prior to slaughter. In contrast, tissue samples of pigs can be used to detect disease using qPCR methods.

Whole Genome Sequencing Shows that African Swine Fever Virus Genotype IX Is Still Circulating in Domestic Pigs in All Regions of Uganda.

Blood samples were collected from pigs at six abattoirs in the Kampala, Uganda metropolitan area from May 2021 through June 2022, and tested for African swine fever virus. Thirty-one samples with cycle threshold values < 26 from pigs with different geographic origins, clinical and pathologic signs, and Ornithodoros moubata exposure underwent whole genome sequencing. The p72 gene was used to genotype the isolates, and all were found to be genotype IX; whole genome sequences to previous genotype IX isolates confirmed their similarity. Six of the isolates had enough coverage to evaluate single nucleotide polymorphisms (SNPs). Five of the isolates differed from historic regional isolates, but had similar SNPs to one another, and the sixth isolate also differed from historic regional isolates, but also differed from the other five isolates, even though they are all genotype IX. Whole genome sequencing data provide additional detail on viral evolution that can be useful for molecular epidemiology, and understanding the impact of changes in genes to disease phenotypes, and may be needed for vaccine targeting should a commercial vaccine become available. More sequencing of African swine fever virus isolates is needed in Uganda to understand how and when the virus is changing.

An Investigation of Burkholderia pseudomallei Seroprevalence in Market Pigs Slaughtered at Selected Pig Abattoirs in Uganda.

Burkholderia pseudomallei is a Gram-negative bacterium that causes melioidosis, a disease of humans and animals. It is primarily transmitted through direct contact with contaminated soil and surface water. The epidemiology of this pathogen in Africa, including Uganda, is largely unknown. The objectives of this study were to estimate the seroprevalence of B. pseudomallei in pigs slaughtered in central Uganda and to identify potential hotspots for this pathogen in the country. A total of 1035 pig sera were analyzed for serological responses to B. pseudomallei with type A and type B LPS using OPS type A and OPS type B ELISAs. Of the 1035 samples, 75 (7.25%, 95% CI: 5.8-9%) were seropositive to the OPS-A ELISA using a two standard deviations (SD) cutoff and 19 (1.84%, 95% CI: 1.2-2.9%) at 3 SD. For the OPS-B ELISA, 93/1035 (8.99%, 95% CI: 7.4-10.9%) were seropositive at the 2 SD cutoff, and 28/1035 (2.71%, 95% CI: 1.9-3.9%) at the 3 SD cutoff. Pigs slaughtered in central Uganda were exposed to B. pseudomallei, and there is a higher seroprevalence in the rainy months. Public health awareness campaigns about melioidosis may be needed.

Seromonitoring of brucellosis in goats and sheep slaughtered at an abattoir in Kampala, Uganda.

We conducted a cross-sectional serologic study at Kampala City abattoir in Uganda on 287 small ruminants (221 goats and 66 sheep) to determine the seroprevalence of brucellosis. The samples were tested using a modified rose bengal test (mRBT) and an indirect ELISA (iELISA). Small ruminant Brucella spp. seropositivity was 18 of 287 (6.3%) by mRBT and 19 of 287 (6.6%) by iELISA. The prevalence of brucellosis by mRBT was non-significantly higher in goats (17 of 221; 7.7%) than in sheep (1 of 66, 1.5%; p = 0.069), and also non-significantly higher by the iELISA in goats (18 of 221; 8.1%) than in sheep (1 of 66, 1.5%; p = 0.057). Brucellosis in slaughtered goats and sheep is a public health hazard to abattoir workers and consumers that calls for control and eradication measures at the farm level, given that testing is not carried out routinely at slaughter points.

Epidemiological Dynamics of Extended-Spectrum ß-Lactamase- or AmpC ß-Lactamase-Producing Escherichia coli Screened in Apparently Healthy Chickens in Uganda.

The dynamics of extended-spectrum ß-lactamase- (ESBL-) and AmpC ß-lactamase-producing bacteria (which are deadly groups of antimicrobial-resistant bacteria) have not been well understood in developing countries. This raises major concerns to antimicrobial resistance (AMR) control. We investigated the prevalence and factors linked to the fecal carriage of ESBL- or AmpC-producing Escherichia coli (ESBL-/AmpC-EC) in commercial chickens. Cloacal swabs from 400 birds were sampled and submitted to the Central Diagnostic Laboratory for ESBL-/AmpC-EC screening by culture methods using MacConkey agar supplemented with cefotaxime. Epidemiological data were collected using a structured questionnaire and plausible risk factor analyses prepared by R software using X 2 test and logistic regression modeling. Results showed that the prevalence of ESBL-/AmpC-EC was 17.5%. Univariable screening hypothesized that carriage was probably influenced by a type of commercial chicken, geographical location, age group, flock size, and housing system (p < 0.05). Modeling exposed that broiler birds were at a higher risk of being ESBL-/AmpC-EC carriers (COR = 9.82, CI = 3.85-25.07). Birds from Wakiso Town Council (COR = 4.89, CI = 2.04-11.72) and flocks of 700-1200 birds were also at a higher risk of harboring ESBL-/AmpC-EC (COR = 2.41, CI = 1.11-5.23). Birds aged 4 months and below were more susceptible to ESBL-/AmpC-EC carriage compared with those aged 1 month and below being 6.33 times (CI = 1.65-24.35) likely to be carriers. The occurrence of ESBL-/AmpC-EC in flocks suggests possible treatment failures while managing colibacillosis. Consequently, injudicious antimicrobial use should be replaced with an accurate diagnosis by bacterial culture and sensitivity testing so as to circumvent AMR emergence, spread, and associated losses.

A retrospective analysis of antimicrobial resistance in pathogenic Escherichia coli and Salmonella spp. isolates from poultry in Uganda.

There are increasing reports of antimicrobial treatment failures for bacterial diseases of poultry in Uganda. The paucity of data on antimicrobial resistance (AMR) of pathogenic bacteria in Uganda is a major setback to AMR control. This study investigated the occurrence of fowl typhoid, colibacillosis, and AMR in associated pathogens from 2012 to 2018. Laboratory records from the Central Diagnostic Laboratory (CDL), a National Veterinary Diagnostic Facility located at Makerere University, were reviewed. Archived isolates of the causative bacteria for the two diseases were also evaluated for AMR. The frequencies of the two disease conditions, their clinical and necropsy presentations and the demographic data of the diagnostic samples were summarized from the records. Archived bacterial isolates were revived before antimicrobial susceptibility testing. This was done on Mueller Hinton agar using the disk diffusion method, against 16 antimicrobials of medical and veterinary importance according to the Clinical Laboratory Standards Institute guidelines. A total of 697 poultry cases were presented for bacteriological investigations in the review period. Colibacillosis and salmonellosis had prevalence rates of 39.7% (277/697) and 16.2% (113/697), respectively. A total of 63 and 92 isolates of Escherichia coli and Salmonella spp., respectively, were archived but 43 (68.3%) E. coli and 47 (51.1%) Salmonella spp. isolates were recovered and evaluated for AMR. Multidrug resistance was more frequent in E. coli (38; 88.4%) than salmonellae (25; 53.2%), (p < 0.001). The high prevalence of colibacillosis, salmonellosis and the AMR of associated pathogens warrants immediate institution of appropriate disease control measures.