Zoonotic Dis., Volume 4, Issue 4 (December 2024) – 9 articles

Bats and rodents serve as reservoirs for numerous zoonotic pathogens, including species of Trypanosoma and Leishmania. Domestic rats host the flea-transmitted Trypanosoma (Herpetosoma) lewisi, which can be associated with humans, particularly young or immunocompromised individuals. Using Fluorescent Fragment Length Barcoding (FFLB) and phylogenetic analyses based on SSU rRNA sequences, we identified two Herpetosoma species, T. lewisi-like and T. musculi-like species, in bats of different families inhabiting rooftops and peridomestic structures in Brazil (44%, 107 bats examined) and Venezuela (50%, 52 bats examined). These species are typically associated with Rattus spp. (domestic rats) and Mus musculus (house mice), respectively. Furthermore, bats were co-infected with up to five other species, including Trypanosoma dionisii, Trypanosoma cruzi marinkellei, and isolates from the Trypanosoma Neobat clade, all strongly associated with bats, and Trypanosoma cruzi and Trypanosoma rangeli, known to infect various mammals, including humans. Therefore, our findings expand the known host range of Herpetosoma to bats, marking the first report of potential spillover of Herpetosoma trypanosomes from rodents to bats and underscoring the potential for the cross-species transmission of flea-borne trypanosomes. These results highlight the need for a One Health approach to assess infection risks associated with trypanosome spillover from synanthropic rodents and bats to humans. Full article

Highly pathogenic avian influenza (HPAI) surveillance for influenza A virus (IAV) in the United States is conducted using a National Animal Health Laboratory Network (NAHLN) real-time reverse transcriptase–polymerase chain reaction (rRT-PCR). Samples showing the presence of IAV are confirmed and characterized at the national reference laboratory. During the H5N1 HPAI outbreak in 2022, our laboratory reported the detection of IAV in a PA commercial chicken flock using rRT-PCR targeting the matrix gene, which was negative for the H5/H7 subtypes. IAV was not detected by additional sampling of the birds the following day with rRT-PCR. The virus detected was characterized as a human seasonal H3N2 with whole-genome sequencing (WGS). Further investigation revealed that the collector who visited the farm was diagnosed with an IAV infection. This case report emphasizes the importance of farm biosafety and biosecurity, of conducting regular reviews of worker safety protocols, and of advanced molecular techniques like WGS for viral characterization and epidemiology. Full article

Halicephalobus gingivalis (H. gingivalis) is a very rare opportunistic cause of fatal meningoencephalomyelitis in equids but may also cause parasitic infections in exposed humans via zoonotic transmission (from animals to humans). We herein report a 39-year-old veterinarian who was exposed to aspirated gastric contents while inserting a nasogastric tube into a horse with signs of uveitis. This procedure requires application of oral suction to the end of the tube to ensure correct placement. Histopathology of the horse’s enucleated eye later revealed H. gingivalis infection, and the horse developed acute kidney injury, ataxia, and other signs of neurological disease. The horse later progressed to death despite supportive care and administration of the broad-spectrum antiparasitic, ivermectin. Two months later, the veterinarian received prophylactic ivermectin consisting of two 200-mcg/kg doses. The patient reported feeling well and was without any systemic or focal signs or symptoms prior to this prophylactic treatment and continued feeling well when followed up at 4 months post exposure. Blood work was unremarkable, with no eosinophilia (eosinophils 0.1 × 10⁹/L, normal <0.4 × 10⁹/L). Meticulous hand hygiene and alternatives to unprotected oral suction should be considered in veterinary medicine as the potentially increasing risk of occupational exposure to zoonotic helminthiases makes this a public health concern. Full article

Background: Environmental changes impact bat–human interactions, heightening concerns of pathogen spillover and highlighting the need to understand human–bat interactions in the context of ecosystems. The objective of this study was to assess factors associated with human contact with bats in communities living near bat roosts in Northern Tanzania. Methods: A cross-sectional survey was used to investigate the factors associated with human contact with bats. Utilizing a standardized questionnaire administered through face-to-face interviews, relevant data were collected from respondents living in or near regions characterized by high bat density. Descriptive analyses followed by bivariate and multivariate analyses were performed to assess the association between the investigated factors and the outcome variable of interest, contact with bats. Results: Data were collected from 325 respondents. Of the respondents, 57.5% (187/325) reported bat contact, and only 4% believed bats can transmit rabies. The following factors were significantly associated with human–bat contact: being unaware that bats can transmit diseases like rabies (AOR = 8.63, CI = 1.04, 71.43, p = 0.045), feeling safe to handle bats with bare hands (AOR = 3.47, CI = 1.71, 7.05, p < 0.001), not washing hands thoroughly after bat bite or scratch (AOR = 2.43, CI = 1.29, 4.59, p = 0.006), using water from ponds, rivers or wells (AOR = 5.58, CI = 3.17, 9.79, p <0.001), age > 45 years (AOR = 1.77, CI = 1.0, 3.14, p = 0.047) and a low level of education (AOR = 5.86, CI = 2.97, 11.57, p <0.001). Conclusion: The study findings highlight the key factors to be targeted when developing strategies aimed at improving the community’s knowledge of the potential risks of zoonotic infectious diseases associated with bats and reducing the likelihood of human–bat contact and the related public health risks in communities living near bat roosting sites in Tanzania. Full article

Ticks are obligate hematophagous ectoparasites notorious for their role as vectors of pathogens that affect humans and animals, particularly relative to the propagation of emerging infectious diseases (EIDs). Two important factors facilitating the role of ticks in the propagation of EIDs are their potential for the development of resistance to acaricides and the expansion of nonindigenous tick species into new geographic regions. The acquisition of acaricide resistance enables tick populations to be less susceptible to vector control programs. Expansion of the geographic distribution of tick populations increases the likelihood of access to new host species as well as new pathogens. Understanding of the microbiome of ticks continues to evolve, providing critical insights into tick biology. The tick microbiome largely comprises endosymbionts, pathogenic organisms, and commensal bacteria. Endosymbionts are highly preserved and vertically transmitted in ticks from mother to offspring, and their role in the survival of ticks is well recognized. Similarly, the role of ticks as vectors of pathogens is well established. However, commensal bacteria in ticks are acquired from the environment and while ingesting a blood meal. Because many tick species spend most of their lifetime off the hosts, it can be assumed that the richness and diversity of commensal bacteria are highly variable and dependent on the ecosystem in which the tick exists. This mini-review identifies some of the critical data gaps relevant to the role of and influence of commensal bacteria on the vectorial capacity of ticks. As ticks move into new habitats, are locally acquired commensal bacteria playing a role in adaptation to the new habitat? Apart from the conventionally understood mechanisms of acaricide resistance in ticks, are the commensal bacteria influencing the development of acaricide resistance at the population level? Full article

SARS-CoV-2 rapidly mutated, causing different waves of outbreaks worldwide. Bhutan experienced three major outbreaks of COVID-19 before experiencing the outbreak driven by the Omicron variant in January 2022. The data collected by the National Outbreak Investigation and Surveillance Team during the Delta variant-driven outbreak and Omicron outbreak were accessed and analyzed. The data were analyzed using R statistical software. Descriptive analysis was carried out for the entire dataset and the statistical comparison between the two outbreaks was carried out using student’s t-test and Pearson’s chi-square test. During the Delta variant-driven outbreak, a total of 1648 cases were reported, with a daily average of 13 cases. The highest one-day case number reported was 99. On the contrary, within 33 days, a total of 3788 cases were reported with a daily average of 115 cases during the Omicron outbreak. The highest one-day case number reported was 312. The median incubation period was 3 days (range = 0–18 days) and 1 day (range = 0–14 days) during the Delta and Omicron-driven outbreaks, respectively. The number of symptomatic cases was significantly higher during the Delta outbreak (p-value < 0.0001). Of the total cases reported during the Delta outbreak, 1175 (71.3%) had received a single dose of the vaccine, 79 (5%) received two doses, while 394 (24%) were unvaccinated. During the Omicron outbreak, 1957 (52%) cases had received their booster (third dose), 904 (23.8%) received two doses and only 40 (1%) received a single dose of the vaccine. The number of unvaccinated cases was 887 (23.4%), of which 375 (10%) were children below 12 years. Our findings corroborate the enhanced transmissibility of the Omicron variant as reported elsewhere. We report significantly less symptomatic cases during the Omicron outbreak. Further, our data show that the incubation period for the Omicron variant is shorter compared to the Delta variant (p-value < 0.0001). Full article

The aim of this study was to characterize the antimicrobial resistance phenotype and genotype of non-typhoidal Salmonella spp. isolated in Luanda, Angola. Between 2013 and 2015, human clinical samples, food, and environmental samples (n = 290) were collected at different regions of Luanda city and screened for the presence of Salmonella spp. Bacterial isolates were preliminarily identified using the API 20E Kit, and their identification was confirmed using PCR and serotyping. All Salmonella spp. isolates were tested by minimum inhibitory concentration against 19 antimicrobials. The isolates were also screened using PCR for the presence of resistance genes (bla_OXA-1, bla_SHV, bla_TEM, sul1, sul2, sul3, qnrA, qnrB, qnrS, qnrC, qnrD, aac(6′)-Ib, dfrIa [targeting dfrA1, dfrA5, dfrA15, dfrA15b, dfrA16, dfrA16b] and dfrA12, cmlA, and floR) and typed using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Salmonella enterica non-typhoidal was detected in 21.3% of the clinical samples (n = 32/150), 11.1% of the food samples (n = 10/90), and 26% of the environmental samples (n = 13/50). Serotyping revealed that the monophasic variant of Salmonella Typhimurium (Salmonella enterica serovar 4,[5],12:i:-) was detected in 38.1% of the samples. Moreover, serovar Salmonella Enteritidis was the second most frequent. Only 7.3% of the isolates were resistant to at least one antimicrobial. Furthermore, isolates from different origins (clinical, environmental, and food) were associated with the same lineages, Salmonella Enteritidis ST11 and S. enterica ser. Typhimurium ST313. The detection of S. enterica serovar 4,[5],12:i:- in different settings reinforces the need for a One Health approach to control this zoonosis in Angola. Full article

A comparative medicine approach, whereby similarities and differences in biology between human and veterinary species are used to enhance understanding for the benefit of both, is highly relevant to the development of viral vaccines. Human and equine influenza share many similarities in pathogenesis and immune responses. The DNA vaccine approach offers potential advantages for responding rapidly and effectively to outbreaks or pandemics in both humans and animals, especially in under-resourced regions. The European and American vaccine regulatory authorities require demonstration of vaccine efficacy in animal models. However, mice, the most widely used model, are not naturally infected with influenza viruses, resulting in different pathobiology. Additionally, mice as a model for DNA vaccine testing appear to overestimate the humoral immune response compared to other mammalian species. In this review, we propose that testing of DNA vaccines against influenza type A viruses (and other shared pathogens) in the horse can provide valuable knowledge for the development of human DNA vaccines. Full article

Some Corynebacterium strains produce toxins that are similar to those produced by Corynebacterium diphtheriae, leading to human infections that are often transmitted through zoonotic diseases. A novel species, which is formerly classified as Corynebacterium ulcerans lineage II, was recently re-evaluated and renamed “Corynebacterium ramonii sp. nov.”. We isolated C. ramonii from a human skin ulcer in Japan in 2023 (KCU0303-001) and identified it as ST344 using a genomic analysis. In addition, C. ramonii KPHES-18084 (ST344) and six strains of C. ulcerans (ST337/ST1011) were isolated from the oral cavities of 7/208 rescued cats (3.4%). The human ulcer strain KCU0303-001 and the rescued cat strain KPHES-18084 were found to be ST344 and closely related clones by core-genome and pan-genome analyses, suggesting that ST344 may be endemic to both clinical and companion animals in Japan. In support of this finding, another clinical isolate of ST344 (TSU-28 strain) was reported in Japan in 2019. Although ST337 is the most common C. ulcerans infection, the second most recent clinical isolate of C. ramonii, ST344, might be increasing; therefore, further genomic surveillance is required to monitor C. ramonii and C. ulcerans infections. Full article