This study investigated the usefulness of a two-serotype dengue mathematical model to gain insights into the effects of antibody-dependent enhancement and temperature on dengue transmission dynamics in the presence of vaccination and Wolbachia-carrying mosquitoes. In particular, the effects of temperature on the mosquito death and maturation rates in secondary infections were examined. A deterministic mathematical model was formulated and analysed to address this problem. The results suggest that controlling the population of aquatic mosquitoes is appropriate for reducing the incidence of secondary infections. Furthermore, the wAu Wolbachia strain was more effective in reducing secondary infections.
Disease dynamics are influenced by changes in the environment. In this study, unreported cases (U), environmental perturbations, and exogenous events are included in the epidemic Susceptible–Exposed–Infectious–Unreported–Removed model with time delays. We examine the process of switching from one regime to another at random. Ergodicity and stationary distribution criteria are discussed. A Lyapunov function is used to determine several conditions for disease extinction. The spread of a disease is affected when transitioning from one random regime to another via sudden external events, such as hurricanes. The model and theoretical results are validated using numerical simulations.
Typhoid fever is an important health issue in developing countries, and the pathogenicity of Salmonella enterica serovar Typhi (S. ser. Typhi) depends on the presence of different virulence factors. Therefore, this study aimed to investigate the spread of virulence genes among S. Typhi isolates from patients with typhoid fever in Baghdad, Iraq. Sixty S. Typhi isolates were collected from several hospitals in Baghdad and identified using VITEK-II and confirmed by polymerase chain reaction (PCR) to detect the 16S rRNA gene. After testing their susceptibility to different antimicrobials (via the disk diffusion method), we found the highest resistance rates (100 %) were to ampicillin, piperacillin, cefotaxime, and ceftriaxone. The highest sensitivity rates (100 %) were to ertapenem, imipenem, meropenem, and sulfamethoxazole/trimethoprim. The presence of genes encoding for virulence in S. Typhi isolates was tested by conventional PCR. The results showed that out of 60 isolates, 59 (98.3 %), 59 (98.3 %), 58 (96.7 %), and 60 (100 %) were positive for viaB, staA, cdtB, and orfL genes, respectively. The sequencing of PCR products (viaB, staA, cdtB, and orfL genes) was carried out at the Macrogen Company (Seoul, Korea). The sequences were compared with nucleotide sequences in the BLAST GenBank database, and data obtained from the sequencing of these virulence genes were submitted to GenBank under different accession numbers. A phylogenetic analysis of the 16S rRNA gene sequence found a high similarity between local sequences and the closely related sequences of genes in GenBank. The presence of the viaB, staA, cdtB, and orfL virulence genes in nearly all of the isolates under examination suggests that they play an important role in the pathogenicity of local isolates.