Molecular characterization of Newcastle disease virus obtained from Mawenzi live bird market in Morogoro, Tanzania in 2020-2021.

Newcastle disease (ND) is among the most important poultry diseases worldwide. It is the major threat to poultry production in Africa and causes major economic losses for both local and commercial chickens. To date, half of ND class II genotypes have been reported in Africa (I, IV, V, VI, VII, XI, XIII, XIV, XVII, XVIII, and XXI). The information on the circulating NDV genotypes is still scarce despite the endemic nature of ND in most countries on the African continent.A total of 659 oro-cloacal swabs were collected from local chickens in Mawenzi live bird market located in Morogoro, Tanzania, between June 2020 and May 2021. Newcastle disease virus was detected by using reverse transcription real-time polymerase chain reaction (RT-qPCR) and conventional PCR followed by sequencing of PCR products. The prevalence of NDV in the surveilled live bird markets was 23.5%. Sequencing and phylogenetic analysis revealed the presence of sub-genotype VII.2. The detected sub-genotype VII.2 has phylogenetic links to Zambian NDV strains implying a Southeast dissemination of the virus, considering that it was first detected in Mozambique. This study underscores the need of active NDV surveillance to determine the distribution of this NDV genotype in the country and monitor its spread and contribution to the emergence of new ND viruses.

Socioecological systems analysis of potential factors for cholera outbreaks and assessment of health system's readiness to detect and respond in Ilemela and Nkasi districts, Tanzania.

BACKGROUND: Cholera outbreaks are a recurrent issue in Tanzania, with Ilemela and Nkasi districts being particulary affected. The objective of this study was to conduct a socio-ecological system (SES) analysis of cholera outbreaks in these districts, identifying potential factors and assessing the preparedness for cholera prevention and control. METHODS: A cross-sectional study was carried out in Ilemela and Nkasi districts of Mwanza and Rukwa regions, respectively in Tanzania between September and October 2021. A SES framework analysis was applied to identify potential factors associated with cholera outbreaks and assess the readiness of the districts to cholera prevention and control. RESULTS: Ilemela is characterised by urban and peri-urban ecosystems while Nkasi is mainly rural. Cholera was reported to disproportionately affect people living along the shores of Lake Victoria in Ilemela and Lake Tanganyika in Nkasi, particularly fishermen and women involved infish trading. The main potential factors identified for cholera outbreaks included defecation in the shallow ends and along the edges of lakes, open defecation, bathing/swimming in contaminated waters and improper waste disposal. The preparedness of both districts for cholera prevention and response was found to be inadequate due to limited laboratory capacity, insufficient human resources, and budget constraints. CONCLUSION: People of Ilemela and Nkasi districts remain at significant risk of recurrent cholera outbreaks and the capacity of the districts to detect the disease is limited. Urgent preventive measures, such as conducting considerable community awareness campaigns on personal hygiene and environmental sanitation are needed to alleviate the disease burden and reduce future cholera outbreaks.

Knowledge, attitude, and preventive practices toward rodent-borne diseases in Ngorongoro district, Tanzania.

In addition to their economic significance, rodents are hosts and transmit diseases. Most of rodent-borne diseases are endemic in rural Africa and sporadically lead to epidemics. Ngorongoro district is inhabited by humans, livestock, and wild animals. Therefore, a cross-sectional study was conducted to assess the level of knowledge, attitudes, and practices toward rodent-borne diseases among communities. The study used 3 focus groups, 20 key informant interviews, and the questionnaire (N=352) to collect data. The study found that 8.52% of respondents had good knowledge, 35.5% had a positive attitude and 94.3% had good practices toward rodent-borne diseases. The study revealed that only 28.13% of participants were aware of rodent-borne zoonoses. The majority of them (77.27%) believe that rodents are pests that destroy crops and do not transmit pathogens. Moreover, the results showed that the majority of them (82.9%) live in dilapidated huts that serve as rodent breeding places. Additionally, except for education and religion, the level of knowledge had no significant relationship with most of the participants' demographic variables. When compared to individuals who didn't attend school, those with secondary education (OR=7.96, CI=1.4-45.31, P=0.017) had greater knowledge of rodent-borne diseases and management. Similarly, to how attitude and practice were found to be considerably (r=0.3216, P=0.000) positively correlated, general knowledge and general practice scores were found to be significantly (r=0.1608, P=0.002) positively correlated. Despite showing good practices, the communities still lack knowledge of rodent-borne zoonosis. Rodent-borne disease education should be considered in Ngorongoro and other places.

Knowledge, attitudes and practices on rift valley fever among pastoral and agropastoral communities of Ngorongoro in the rift valley ecosystem, Tanzania, conducted in 2021/2022.

Epidemics of Rift Valley fever (RVF), a mosquito-borne zoonotic disease caused by RVF virus, have been linked to exceptionally heavy rainfall and widespread flooding. The disease is endemic in most African countries and pose a major global health risk. Given that the disease was reported in various districts of Tanzania, we hypothesized a lack of knowledge about RVF epidemiology among agropastoral and pastoral communities. The research took place in a period of 7 months, from July, 2021 to January, 2022. The aim of this study was to assess the knowledge, attitudes, and practices (KAP) among the agropastoral and pastoral communities of Ngorongoro district towards RVF. The survey employed a mixed method system, which included 3 focus groups (each comprised 12 individuals), 20 key informant interviews and administration of questionnaire (N = 352) in agropastoral and pastoral community members of Ngorongoro district. The relationship between demographic characteristics and communities' knowledge, attitudes, and practices regarding RVF was observed using a multiple logistic regression model. A total of 352 participants were interviewed, with the majority (67.61%) being male and 32.39% being female, majority (39.5%) attending primary school, and majority (58.2%) being pastoralists. The findings showed that only 36.1%, 38.64% and 16.19% of participants had good knowledge, positive attitude and good practices regarding RVF respectively. Significant demographic factors related with knowledge included: gender (OR = 1.9, CI = 1.03-3.56, P = 0.041), education levels (primary: OR = 3.97, CI = 2-8.16, P = 0.000; secondary: OR = 15.27, CI = 5.5-46.23, P = 0.000 and college: OR = 34. 23, CI = 5.4-67.22, P = 0.000), and locality (Pinyinyi: OR = 0.14, CI = 0.05-0.38, P = 0.000 and Sale: OR = 0.14, CI = 0.04-0.44, P = 0.001). Male participants showed significant positive attitude towards RVF compared to female (OR = 2.37, CI = 1.35-4.17, P = 0.003). Individuals with formal education showed a significant positive attitude toward RVF compared to informal (OR>1, P<0.05). Agropastoral members showed a significant negative attitude toward RVF compared to pastoralists (OR = 0.51, CI = 0.26-0.99, P = 0.048). The calculated RVF prevention practices values were insignificantly (P = 0.853) correlated with knowledge values. The significant correlation between knowledge and attitude, as well as attitude and practice were found (P<0.05). In general, the study revealed poor knowledge, negative attitude and poor practices of communities towards RVF. The lack of regular education programs to make the communities aware of the disease was implicated for these findings. This recommends that provision of health education should be a long-term practice among agropastoral and pastoral communities in order to prevent further RVF outbreaks in Tanzania.

Genetic Diversity of Newcastle Disease Virus Involved in the 2021 Outbreaks in Backyard Poultry Farms in Tanzania.

Newcastle disease virus is a significant avian pathogen with the potential to decimate poultry populations all over the world and cause enormous economic losses. Distinct NDV genotypes are currently causing outbreaks worldwide. Due to the high genetic diversity of NDV, virulent strains that may result in a lack of vaccine protection are more likely to emerge and ultimately cause larger epidemics with massive economic losses. Thus, a more comprehensive understanding of the circulating NDV genotypes is critical to reduce Newcastle disease (ND) burden. In this study, NDV strains were isolated and characterized from backyard poultry farms from Tanzania, East Africa in 2021. Reverse-transcription polymerase chain reaction (RT-PCR) based on fusion (F) gene amplification was conducted on 79 cloacal or tracheal swabs collected from chickens during a suspected ND outbreak. Our results revealed that 50 samples out 79 (50/79; 63.3%) were NDV-positive. Sequencing and phylogenetic analyses of the selected NDV isolates showed that 39 isolates belonged to subgenotype VII.2 and only one isolate belonged to subgenotype XIII.1.1. Nucleotide sequences of the NDV F genes from Tanzania were closely related to recent NDV isolates circulating in southern Africa, suggesting that subgenotype VII.2 is the predominant subgenotype throughout Tanzania and southern Africa. Our data confirm the circulation of two NDV subgenotypes in Tanzania, providing important information to design genotype-matched vaccines and to aid ND surveillance. Furthermore, these results highlight the possibility of the spread and emergence of new NDV subgenotypes with the potential of causing future ND epizootics.

Efficiency, sensitivity and specificity of a quantitative real-time PCR assay for Tilapia Lake virus (TiLV).

Tilapia lake virus (TiLV) is an emerging viral pathogen of tilapiines worldwide in wild and farmed tilapia. TiLV is an orthomyxo-like, negative sense segmented RNA virus, belonging to genus Tilapinevirus, family Amnoonviridae. Here we developed a quantitative real-time PCR (qRT-PCR) assay testing primer sets targeting the 10 segments of TiLV. Sensitivity, specificity, efficiency and reproducibility of these assays were examined. Detection sensitivity was equivalent to 2 TCID50/ml when tested on supernatants from cell culture-grown TiLV. Specificity tests showed that all primer sets amplified their respective TiLV segments, and standard curves showed linear correlation of R2 > 0.998 and amplification efficiencies between 93 % and 98 %. Intra- and inter-assay coefficients of variation (CV %) were in the range of 0.0 %- 2.6 % and 0.0 %- 5.9 %, respectively. Sensitivity tests showed that primer sets targeting segments 1, 2, 3 and 4 had the highest detection sensitivities (100.301 TCID50/ml). The qRT-PCR used for detection of viral genome in TiLV infected organs gave virus titers equivalent to 3.80 log10, 3.94 log10 and 3.52 log10 TCID50/ml for brain, kidney and liver tissues, respectively as calculated on the basis of Ct values. These findings suggest that primer optimization for qPCR should not only focus on attaining high amplification efficiency but also sensitivity comparison of primer sets targeting different viral segments in order to develop a method with the highest sensitivity.

Aedes aegypti abundance, larval indices and risk for dengue virus transmission in Kinondoni district, Tanzania.

BACKGROUND: Tanzania has experienced periodic dengue outbreaks with increased incidence since 2010. However, there is limited information on vector dynamics and transmission risk in most parts of the country. This study was conducted to determine Aedes mosquito abundance, larval indices and dengue virus infection rate as risk indicators for DENV transmission in Kinondoni district, Dar es Salaam, Tanzania. METHODS: A cross-sectional study was conducted in three wards of Kinondoni district in Tanzania between December 2019 and January 2020. In each ward, three streets were randomly selected for adult and immature mosquito sampling. The adult mosquitoes were collected using Mosquito Magnet traps, while mosquito larvae and pupae were inspected in water-holding containers in the selected household compounds. The detection of dengue virus (DENV) in female Aedes mosquitoes was done using a one-step reverse transcription-polymerase chain reaction (RT-PCR) method. RESULTS: Of the 1416 adult female mosquitoes collected, Ae. aegypti accounted for 16.8% (n = 238). A total of 333 water-holding containers were inspected and 201 (60.4%) had at least an Aedes larvae or pupae. Water-holding containers supporting the breeding of Aedes larvae and pupae included discarded car tires, flowerpots and small and large plastic containers. The overall House Index, Container Index and Breteau Index were 55.1%, 60.4% and 114.2, respectively. None of the 763 female Aedes mosquitoes tested by RT-PCR was found to be infected with DENV. CONCLUSION: The presence and abundance Ae. aegypti mosquitoes and the large proportion of water-holding containers infested with the mosquito larvae and pupae put residents of Kinondoni district at high risk of DENV transmission. Our findings emphasize the need for continuous mosquito vector surveillance and control to prevent the possibility of future DENV outbreaks in Tanzania.

Tilapia Lake Virus Does Not Hemagglutinate Avian and Piscine Erythrocytes and NH4Cl Does Not Inhibit Viral Replication In Vitro.

Tilapia lake virus (TiLV) is a negative-sense single-stranded RNA (-ssRNA) icosahedral virus classified to be the only member in the family Amnoonviridae. Although TiLV segment-1 shares homology with the influenza C virus PB1 and has four conserved motifs similar to influenza A, B, and C polymerases, it is unknown whether there are other properties shared between TiLV and orthomyxovirus. In the present study, we wanted to determine whether TiLV agglutinated avian and piscine erythrocytes, and whether its replication was inhibited by lysosomotropic agents, such as ammonium chloride (NH4Cl), as seen for orthomyxoviruses. Our findings showed that influenza virus strain A/Puerto Rico/8 (PR8) was able to hemagglutinate turkey (Meleagris gallopavo), Atlantic salmon (Salmo salar L), and Nile tilapia (Oreochromis niloticus) red blood cells (RBCs), while infectious salmon anemia virus (ISAV) only agglutinated Atlantic salmon, but not turkey or tilapia, RBCs. In contrast to PR8 and ISAV, TiLV did not agglutinate turkey, Atlantic salmon, or tilapia RBCs. qRT-PCR analysis showed that 30 mM NH4Cl, a basic lysosomotropic agent, neither inhibited nor enhanced TiLV replication in E-11 cells. There was no difference in viral quantities in the infected cells with or without NH4Cl treatment during virus adsorption or at 1, 2, and 3 h post-infection. Given that hemagglutinin proteins that bind RBCs also serve as ligands that bind host cells during virus entry leading to endocytosis in orthomyxoviruses, the data presented here suggest that TiLV may use mechanisms that are different from orthomyxoviruses for entry and replication in host cells. Therefore, future studies should seek to elucidate the mechanisms used by TiLV for entry into host cells and to determine its mode of replication in infected cells.

Molecular detection of Rift Valley fever virus in serum samples from selected areas of Tanzania.

Rift Valley fever (RVF) is an acute mosquito-borne viral zoonotic disease affecting domestic animals and humans caused by the Rift Valley fever virus (RVFV). The virus belongs to the genus Phlebovirus of the family Bunyaviridae. The main aim of this study was to detect the presence of antibodies to RVFV as well as the virus in the serum samples that were collected from livestock during the 2006/2007 RVF outbreaks in different locations in Tanzania. Analysis of selected samples was done using a RVF-specific inhibition enzyme-linked immunosorbent assay (I-ELISA) and reverse transcription polymerase chain reaction (RT-PCR). Genomic viral RNA was extracted directly from serum samples using a QIAamp Viral RNA Mini Kit (QIAGEN), and a one-step RT-PCR protocol was used to amplify the S segment of RVFV. Positive results were obtained in 39.5% (n = 200) samples using the RVF I-ELISA, and 17.6% (n = 108) of samples were positive by RT-PCR. I-ELISA detected 41 (38.7%), 32 (39.0%), and 6 (50.0%) positive results in cattle, goats, and sheep sera, respectively, whereas the RT-PCR detected 11 (0.2%), 7 (0.2%), and 1 (0.1%) positive results in cattle, goats, and sheep sera, respectively. These findings have demonstrated the presence of RVFV in Tanzania during the 2006/2007 RVF outbreaks. To our knowledge, this is the first report to detect RVFV in serum samples from domestic animals in Tanzania using PCR technique. Therefore, a detailed molecular study to characterize the virus from different geographical locations in order to establish the profile of strains circulating in the country and develop more effective and efficient control strategies should be done.

Socio-economic impact of Rift Valley fever to pastoralists and agro pastoralists in Arusha, Manyara and Morogoro regions in Tanzania.

Rift Valley fever (RVF) is a viral notifiable zoonotic disease primarily of domestic ruminants that causes significant socio-economic impacts. Using the 2006-07 outbreak cases, this study aimed to establish the socio-economic impact of RVF and assessing knowledge, attitude and practice of livestock keepers towards controlling RVF in selected areas of Tanzania. Data were collected in Arusha, Manyara and Morogoro regions using questionnaires, focus group discussions and in-depth interviews with key informants. Results indicate that there was little knowledge on disease (all clinical signs scored <50%) and the difference between the three regions was statistically significant (P = 0.00459). Socio-economic impacts of RVF shown by this study included; animal and human deaths, disruption of livestock market chains, inability of pastoralists to achieve their daily demands, inability to obtain protein leading to malnutrition and monetary loss at individual and national level during control of the disease. These findings have demonstrated low knowledge of the community on RVF, thus, more education and engagement is needed in order to develop more effective and efficient control strategies.