الفهرس 
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Abstract
Encephalitis is defined by the presence of an inflammatory process of the brain in association with clinical evidence of neurologic dysfunction. Of the pathogens reported to cause encephalitis, the majority are viruses. However, despite extensive testing, the etiology of encephalitis remains unknown in most patients. The major challenge for patients with encephalitis is to determine the relevance of an infectious agent, either viruses or other pathogens, identified outside of the Central Nervous System (CNS). These agents may play a role in the neurologic manifestations of illness but not necessarily by directly invading the CNS.
Regarding previous literatures, there is a lack of information regarding the etiology of viral meningitis/encephalitis in Egypt and the Middle East. Accordingly, the meningitis viruses circulating in Egypt are likely to be quiet different than in other areas of the world including the United States and Western Europe, where etiologies of viral meningitis are better established.Since Middle East region is a very well known geographic area for presence of different arboviruses. The presence of arboviruses’ diseases of WNV, Sandfly viruses, RVFV and SINV must be expected.
Climate especially temperature and humidity are major factors in determining: (1)the geographic and temporal distribution of arthropods; (2)characteristics of arthropod life cycles; (3)dispersal patterns of associated arboviruses; (4)the evolution of arboviruses; and (5)the efficiency with which they are transmitted from arthropods to vertebrate hosts.
The primary objective of this study is to report the seroprevalence of specific IgM seroprevalence of specific IgG serop and prevalence rates through detection of IgM and IgG respectively of for five arboviruses. They Virsues are Rift Valley Fever virus (RVFV), Sandfly Naples virus (SFNV), Sandfly Sicilian virus (SFSV), Sindbis virus (SINV), and West Nile virus (WNV) that may cause encephalitis in Egypt.
Secondary objective is to study the factors that may contribute in circulation of the above mentioned arboviruses. Since those arboviruses are known to be circulating in Egypt. Long term study for 2 years, throughout most of the Egyptian governorates through different seasonal distribution may offer a great evidence for different factors affecting arboviral transmission in Egypt.
To reach our objectives, serum samples (acute samples) were collected from 1702 suspected encephalitis patients from eight different fever hospitals all over Egypt through years 1998 and 1999. Fever hospitals were Alexandria fever hospital, Mahala fever hospital, Zagazig fever hospital, Abbassia fever hospital, Imbaba fever hospital, Fayoum fever hospital, Assuit fever hospital, and Aswan fever hospital.
Serum samples were sent to Naval Medical Research unit-3 (NAMRU3) for serological lab testing. Enzyme linked immunosorbent assay (ELISA) has been done for the detection of IgM and IgG for those above mentioned five arboviruses.
Data were analyzed statistically regarding different parameters: age, sex, seasonal distribution and regional distribution.
The results can be summarized in the following points:
1.Overall incidence seroprevalence of specific IgM (positive for IgM) was 44/1702 (2.6%), while overall prevalence (positive for IgG)seroprevalence of specific IgG was 355/1702 (20.8%). The highest incidence seroprevalence of specific IgM11/173 (6.4%) has been shown in the elderly age group 40-<60 years, whereas in age group> 60- years, prevalence was the highest 40/84 (47.6%). seroprevalence of specific IgMIncidence in males was 34/998 (3.4%) while in females was 10/703 (1.4%). Furthermore, the prevalence rate was the same in both genders 206/998 (21%) in males, number of and 149/703 in females (21%).
2.Overall seroprevalence of specific IgM regarding Incidence regarding seasonal distribution was as follow: winter 16/249 (6.4%), autumn 11/291 (3.8%), summer 12/688 (1.7%) and spring 5/473 (1.1%). Different pattern was observed in overall prevalence rate, summer is the highest 138/688 (39%), followed by spring 104/473 (29.3%), then autumn 66/291(18%) and winter 47/249 (13%).Upper and Lower Egypt has the same incidence rates (3.1%): 22/712 and 14/441 respectively, and prevalence rates 173/712 (24%) and 102/441 (23%), respectively.
3.seroprevalence of specific IgM Incidence ratio for individual virus was as follow: RVFV 18/1702 (1.1 %), SFNV 16/1702 (0.9%), SFSV 6/1702 (0.3%), SINV 3/1702 (0.2%), and WNV 2/1702 (0.1%). The results also revealed that the RVFV had the highest incidence prevalence rate in each examined parameter as follow: 6/18 (33%) in age group 40-<60 year. In males 13/18 (73%). In Summer 8/18 (44%) and, in Upper Egypt region was 9/18 (50%).
4.The following tested arboviruses showed the highest seroprevalence of specific IgMincidence rate (positive for IgM) regarding several applied parameters.
(a)In SFNV the highest incidence prevalence rate in each parameter as follow: 5/16 (31%) in age group 6-<18 year. In males 12/16 (75%), in winter 7/16 (44%) and, in Upper Egypt region was 9/16 (59%).
(b)In SFSV had the highest incidence prevalence rate in each parameter as follow: 4/6 (66%) in age group 6-<18 year. In males, 5/6 (83%), in Winter 4/6 (66%) and, in Upper Egypt region was 3/6 (50%).
(c)In SINV had the highest incidence prevalence rate in each parameter as follow: 1/3 (67%) in age group 40-<60 year. In males 3/3 (100%), in winter 3/3 (100%) and 2/3 (76%) in Cairo region.
(d)In WNV had the highest incidence prevalence rate in each parameter as follow: 2/2 (100%) in age group 6-<18 year, 1/2 (50%) in males, 1/ 2 50% in winter and 50% in spring and, 2/2 (100%) in Upper Egypt region.
5.Similarly the results of seroprevalence of specific IgG prevalence ratio of each tested arboviruses ( positive for IgG) have shown that : WNV 234/1702 (13.7%), SFNV 117/1702 (6.9%), SINV 66/1702 (3.9%), SFSV 54/1702 (3.2%) and, RVFV 21/1702 (1.2%).Not so far from the highest incidence prevalence of specific IgM rate, the highest prevalence rate in RVFV regarding the different parameters was as follow : 11/21 (52%) in age group 40-<60 year,17/21( 81%) in males, 9/21 (42%) in Autumn and, 11/22 (52%) in Upper Egypt region.
6.Concerning the other tested arboviruses , the results indicated that the highest detection rate of IgG (prevalence) seroprevalence of specific IgG in these viruses in relation to the different parameters were as follow:
(a)In SFNV, the highest prevalence rate was as follow: 28/117 (24%) in age group 25-<40 year, 65/117 (55% ) in males, 46/117 (39%) in summer and, 64/117 (54%) in Upper Egypt region.
(b)In SFSV had the highest prevalence rate in each parameter as follow: 17/54 (31%) in age group 6-<18 year, 30/54 (55%) in males, 23/54 (42%) in summer and, 27/54 (50%) in Upper Egypt region.
(c)In SINV had the highest prevalence rate in each parameter as follow: 14 /66 (21%) in age group 6-<18 year, 37/66 (56%) in females, 32/66 (48%) in Spring and, 25/66 (36%) in Upper Egypt region.
(d)In WNV had the highest prevalence rate in each parameter as follow: 59/234 (25%) in age group 6-<18 year, 142/234 (60% ) in males, 90/234 (38%) in summer and, 117/234 (50%) in Upper Egypt region.
7.Although previous studies of arboviruses especially WNV, SF viruses, how indicated that they may cause encephalitis and/or meningitis, but in the present study, the statistical analysis of clinical data was insignificant for encephalitis and/or meningitis.
8.In general, we confidently established that from this study:
(a)Climate is a major factor in determining: the geographic and temporal distribution of arthropods and characteristics of arthropod life cycles.
(b)Temperature and Humidity are the components of macroclimate which are likely to have the most important direct effect on vector biology and ecology.
(c)Arthropods for the studied viruses, are found all over Egypt. However, a unified electronic system is needed for better understanding of different mosquito and sandfly species found in the area.
Our prospective plan is to continue surveillance in incidence and prevalence of arboviruses. To reach our goal, we are going to use recent diagnosed samples and using different laboratory assays for sample testing .
Discussion and Conclusion:
1.The five studies arboviruses were found all over Egypt.
2.physician should consider arboviruses as fever causative agents especially in patients had travel history in endemic areas, since in Egypt such illness is often misdiagnosed as “influenza”.
3.Limitations in health systems in endemic areas undoubtedly lead to underestimation of arboviruses’ incidence and related complications. However, improving diagnostics and better understanding of the late secondary results of infection now give a first approximation of the current disease burden from these widespread serious infections.
4.Arboviruses control and prevention remain a high priority, both because of the current disease burden and the significant threat of the re-emergence of these viruses among much larger groups of susceptible populations as recently happened in RVFV in Kafr El Sheikh Governorate.
5.A multi-disciplinary approach is now imperative, and groups need to collaborate in an integrated manner that includes vector control, vaccination programmes, improved therapy strategies, diagnostic tools and surveillance, public awareness, capacity building and improvement of infrastructure in endemic regions.