A Qualitative Evidence of the Breeding Sites of Anopheles arabiensis Patton (Diptera: Culicidae) in and Around Kassala Town, Eastern Sudan.

Anopheles arabiensis Patton (Diptera: Culicidae) is considered the most efficient malaria vector in eastern Sudan. This study aims to characterize the breeding sites of An. arabiensis throughout the year in and around Kassala town, eastern Sudan. Diverse larval habitat types were visited and characterized based on the habitat type and chemical composition. Mosquito larvae were found in many diverse habitats. During the rainy season, rain pools and water bodies created by the seasonal Gash River serve as the main breeding sites. In the dry season, irrigation canals, seepage from water pipes, neglected wells, artificial containers, and man-made ditches serve as the main breeding sites. Breeding water showed a pH of 7.9 and a low concentration of the total dissolved salts. The results of this study may be considered in planning and implementing larval control programs in the area.

Recent outbreaks of rift valley Fever in East Africa and the middle East.

Rift Valley fever (RVF) is an important neglected, emerging, mosquito-borne disease with severe negative impact on human and animal health. Mosquitoes in the Aedes genus have been considered as the reservoir, as well as vectors, since their transovarially infected eggs withstand desiccation and larvae hatch when in contact with water. However, different mosquito species serve as epizootic/epidemic vectors of RVF, creating a complex epidemiologic pattern in East Africa. The recent RVF outbreaks in Somalia (2006-2007), Kenya (2006-2007), Tanzania (2007), and Sudan (2007-2008) showed extension to districts, which were not involved before. These outbreaks also demonstrated the changing epidemiology of the disease from being originally associated with livestock, to a seemingly highly virulent form infecting humans and causing considerably high-fatality rates. The amount of rainfall is considered to be the main factor initiating RVF outbreaks. The interaction between rainfall and local environment, i.e., type of soil, livestock, and human determine the space-time clustering of RVF outbreaks. Contact with animals or their products was the most dominant risk factor to transfer the infection to humans. Uncontrolled movement of livestock during an outbreak is responsible for introducing RVF to new areas. For example, the virus that caused the Saudi Arabia outbreak in 2000 was found to be the same strain that caused the 1997-98 outbreaks in East Africa. A strategy that involves active surveillance with effective case management and diagnosis for humans and identifying target areas for animal vaccination, restriction on animal movements outside the affected areas, identifying breeding sites, and targeted intensive mosquito control programs has been shown to succeed in limiting the effect of RVF outbreak and curb the spread of the disease from the onset.

Validation of PCR for detection and characterization of parasitaemia in massive splenomegaly attributed clinically to malaria infection.

In this study, 101 patients with massive splenomegaly (MS) and 41 with moderate splenomegaly (MoS) from Kassala, Eastern Sudan, were included. The patients were recruited during a peak and the end of a malaria season and during a dry season between 2007 and 2008. Based on clinical findings and exclusion of other causes of MS, the former patients were presumed to be infected with malaria parasite; thus, the condition was termed as massive malarial splenomegaly (MMS). Rapid diagnostic test (RDT) and polymerase chain reaction (PCR) were used for malaria parasite detection. In the MMS group, the parasite rate was 50% and 49% as estimated by microscopy and RDT, respectively. However, the PCR showed higher parasite rate (79.3%, P = 0.000), Plasmodium vivax infection, and mixed infections. The PCR-corrected parasite rate in the MoS and control groups was 73.2% and 3.5%, respectively. The parasite rate as estimated by microscopy was highest at the end of the malaria season and lowest in the dry season; however, the parasite rate estimated by PCR was stable in all study periods. There was significant reduction in spleen size following anti-malaria treatment. In conclusion, the use of PCR had revealed significantly higher parasite rate, P. vivax, and mixed infections in MMS as compared to microscopy, while the RDT was found to be comparable to microscopy and is suggested to complement the use of the latter. The study also disclosed a seasonal variation of patent parasitemia with an overall low parasite count and scarce gametocytaemia in MMS.

Towards a noninvasive approach to malaria diagnosis: detection of parasite DNA in body secretions and surface mucosa.

Invasive procedures for diagnostic or therapeutic purposes bear a relative risk of transmission of serious blood-borne infectious disease. In this study, a noninvasive approach to malaria diagnosis using polymerase chain reaction (PCR) for the detection of parasite DNA in saliva, buccal mucosa and urine (alternative samples) was examined. Saliva, buccal mucosa and urine samples were collected simultaneously with blood samples from 93 patients with microscopically confirmed Plasmodium falciparum infection. Species-specific primers detected the parasite DNA only in blood samples. However, when the PCR analysis was repeated using MSP1 and MSP2 primers in a subgroup of 21 complete sets of samples, the parasite DNA was detected in all except 3 samples, which were found to be negative with the MSP2 primers. Parasite density, body temperature or patient age did not influence the PCR results. In conclusion, P. falciparum parasite DNA was detected equally in saliva, buccal mucosa and urine of malaria patients, regardless of their ages, body temperatures or parasite density. Surprisingly, the parasite DNA was not amplified by species-specific primers in the alternative samples whereas it was in the blood samples.

Habitat stability and occurrences of malaria vector larvae in western Kenya highlands.

BACKGROUND: Although the occurrence of malaria vector larvae in the valleys of western Kenya highlands is well documented, knowledge of larval habitats in the uphill sites is lacking. Given that most inhabitants of the highlands actually dwell in the uphill regions, it is important to develop understanding of mosquito breeding habitat stability in these sites in order to determine their potential for larval control. METHODS: A total of 128 potential larval habitats were identified in hilltops and along the seasonal streams in the Sigalagala area of Kakamega district, western Kenya. Water availability in the habitats was followed up daily from August 3, 2006 to February 23, 2007. A habitat is defined as stable when it remains aquatic continuously for at least 12 d. Mosquito larvae were observed weekly. Frequencies of aquatic, stable and larvae positive habitats were compared between the hilltop and seasonal stream area using chi2-test. Factors affecting the presence/absence of Anopheles gambiae larvae in the highlands were determined using multiple logistic regression analysis. RESULTS: Topography significantly affected habitat availability and stability. The occurrence of aquatic habitats in the hilltop was more sporadic than in the stream area. The percentage of habitat occurrences that were classified as stable during the rainy season is 48.76% and 80.79% respectively for the hilltop and stream area. Corresponding frequencies of larvae positive habitats were 0% in the hilltop and 5.91% in the stream area. After the rainy season, only 23.42% of habitat occurrences were stable and 0.01% larvae positive habitats were found in the hilltops, whereas 89.75% of occurrences remained stable in the stream area resulting in a frequency of 12.21% larvae positive habitats. The logistic regression analysis confirmed the association between habitat stability and larval occurrence and indicated that habitat surface area was negatively affecting the occurrence of An. gambiae larvae. While An. gambiae and An. funestus larvae occurred throughout the study period along the streams, a total of only 15 An. gambiae larvae were counted in the hilltops, and no An. funestus were found. Moreover, no larvae managed to develop into adults in the hilltops, and the density of adult An. gambiae was consistently low, averaging at 0.06 females per house per survey. CONCLUSION: The occurrence of malaria vector larvae in the hilltop area was uncommon as a result of the low availability and high instability of habitats. To optimize the cost-effectiveness of malaria interventions in the western Kenya highlands, larval control should be focused primarily along the streams, as these are likely the only productive habitats at high altitude.

Malaria overdiagnosis and burden of malaria misdiagnosis in the suburbs of central Sudan: special emphasis on artemisinin-based combination therapy era.

Accuracy of diagnosis is central for malaria control. Although microscopy is gold standard in malaria diagnosis, its reliability is largely dependent on user skill. In this study, we evaluated practitioners' clinical and microscopists' technical skills in diagnosis of malaria in central Sudan. In a retrospective study, 3203 blood smears from 95 peripheral health facilities (each represented by a general practitioner [GP] and general microscopist [GM]) were reexamined by expert microscopist. Furthermore, in a prospective study, 410 patients had their malaria diagnosis rechecked by rapid diagnostic test for validation of the microscopic diagnosis. Results showed that the rate of false-positive diagnosis of malaria was 75.6% and false-negative diagnosis was 0.01%. The study disclosed poor skills of the GPs and GMs in malaria diagnosis because 43% of the GPs and 44% of the GMs failed to make a single true-positive malaria diagnosis. The false-positive malaria diagnosis showed bias toward adult females. Economically, the calculated cost of diagnosis and treatment of malaria in Sudan in year 2000 is US$100 million, whereas the calculated cost of true malaria is approximately US$14 million. In conclusion, malaria overdiagnosis was widely recognized in central Sudan, with high economic burden during the era of artemisinin-based combination therapy. Finally, different scenarios were suggested for improvement of malaria diagnosis.

Parasites of the Nile rat in rural and urban regions of Sudan.

In this investigation on endoparasites (helminths) and ectoparasites of the Nile rat (Arvicanthis niloticus Desmarest, 1822), a total of 220 Nile rats were trapped from different regions of Sudan during the period January 2003-January 2006. Examination of different tissues, identification of parasites, effect of these parasites on the organs, the prevalence and intensity of infestation of the parasites and their relation to the habitat of the host, and sex-related infestations were considered. Results showed that the variation among helminth species was wide, especially in those that are transferred by arthropods. No protozoan parasites or distortion in the infected tissues were observed. No examination for Toxoplasma gondii was carried out. Two species of cestodes (Hymenolepis nana, Hymenolepis diminuta), two genera (Raillietina sp. I, Raillietina sp. II) and one unidentified Hymenolepididae were reported. The most prevalent species of cestodes was Raillietina sp. And for nematodes only one species and one genus were recovered (Monanema nilotica and Streptopharagus sp.). Investigation of skin revealed that 83.8% of rats were infested with one or more of ectoparasites; namely, insects and arachnids. This survey also revealed that fleas and lice were the most common ectoparasites that infested the Nile rat. Synanthropic rodents, particularly those living in close association with man, play a significant role in human health, welfare and economy. It has to be stressed that their arthropod ectoparasites are important vectors of pathogenic microorganisms and they can also be important reservoirs for parasitic zoonoses, like trichinellosis and capillariosis. No doubt, the increase in rodent populations could be followed by an increase in zoonotic diseases (Stojcevic et al. 2004, Durden et al. 2000). Rats and mice (commensal and wild) play an important role in public health, being carriers or reservoirs for infectious diseases that can be transmitted to humans (zoonoses). Xenopsylla cheopis is the most important vector of plague and the rickettsial infection murine typhus (Gratz 1999). Man can also acquire the infection through direct contact with infected animals' tissues (WHO 1987). Arvicanthis niloticus, Mastomys natalensis and Rattus rattus are probably the most important and widespread reservoirs of plague in Kenya: 10 percent of all Rattus rattus tested were found to be positive as compared to 12% of the Arvicanthis niloticus (Gratz 1999).