Prevalence of Crytpococcal Infection in Patients Clinically Diagnosed to Have Meningitis in Ethiopia

Cryptococcal meningitis is a fungal infection that causes significant morbidity and mortality worldwide. However, its incidence in Ethiopia is poorly known. The present study was undertaken to determine cryptococcal meningitis in Ethiopian patients diagnosed to have meningitis. Cerebrospinal fluid was collected from 201 patients with meningitis attending two tertiary hospitals for the isolation and characterization of major bacterial pathogens implicated in causing meningitis. Left over sample of each patient was screened for cryptococal antigen using lateral flow Assay. Of the total number of 201 patients 17 (8.5%) were positive for cryptococcal antigenemia of which 8 (47.1%) were male patients while 9 (52.9%) were female patients. In conclusion a high prevalence of cryptococcal meningitis in the present study urges detection and /or isolation and characterization of the pathogen in patients diagnosed to have meningitis regardless of the immune status. Furthermore, in view of the increasing number of cryptococcal infections, rapid, sensitive, and specific diagnosis of cryptococcal disease has become more important than ever in Ethiopian health institutions.


Introduction
Cryptococcal meningitis is an infectious disease that affects predominantly immune compromised hosts causing significant morbidity and mortality. Although cryptococcosis has been recognized for more than 100 years, worldwide spread of HIV infection and other forms of immunesuppression are incriminated as the most important factors for its increase since the 1980's [1]. Currently, it has been estimated that there are about one million new cases of cryptococcosis and at least 600,000 deaths annually worldwide due to HIV-associated cryptococcosis [2]. In sub-Saharan Africa with the highest HIV prevalence, Cryptococcus species has become the leading cause of meningitis, preceding pneumococcal and meningococcal meningitis [3][4][5][6][7][8][9]. The infection accounts 13-44% of all deaths in HIV infected individuals in this geographical region [10][11][12].
Although cryptococcal meningitis is generally thought to be associated with immune-compromised patients (i.e., HIVpositive patients and non-HIV-infected immunocompromised patients), recent studies [13][14][15] showed that its incidence has increased among immunecompetent individuals. Ethiopia being located in sub-Saharan Africa, the morbidly and mortality of cryptococcal meningitis is poorly known. To the best of our knowledge, two case reports [16,17] and three full flagged research articles in HIV infected patients [18][19][20] have been published with regards to cryptococcal infection.
An accurate diagnosis of cryptococcosis is important for its successful treatment. The cost and long duration of the therapy, the risk of developing adverse drug reactions, and possible interactions with concomitant medications all underline the importance of accurate diagnosis of the condition before commencing therapy. Therefore, early identification of cryptococcal infection regardless of the immune status of a host and clinical manifestations is indispensable for appropriate management of the complication.
Demonstrating capsulated yeast by India ink preparation, culture and detection of capsular polysaccharide antigen serologically from various clinical samples (CSF, serum, urine) has been the mainstay for the diagnosis of cryptococcal infections. Although culture is considered as a gold standard for the isolation and characterization of the yeast, fungal culture is not performed in routine clinical laboratory practice in Ethiopia. Currently, the diagnostic tests most commonly used in the developed world for identifying cryptococcal antigen are the latex agglutination test (LA) and the enzyme immunoassay (EIA). These tests are not practiced in clinical laboratories in Ethiopia since they are resource intensive. Therefore, detection of the yeast by less sensitive and non-specific India ink preparation is the commonest test practice in clinical laboratories in Ethiopia. Lack of sensitive and specific test procedures in Ethiopian health institution have been identified as major problem in the under reporting of the infection. Difficulty in differentiating signs and symptoms of cryptococcal meningitis clinically from those of many other forms of meningitis has also hampered the study of cryptococcal meningitis. In line with, the aim of this study was to determine cryptococcal infection in patients diagnosed to have meningitis regardless of their clinical manifestations and immune status.

Study Patients
Patients diagnosed to have meningitis were enrolled between September 2006 and August 2007 from the outpatient department of Tikur Anbessa (Black Lion) and Yekatit twelve teaching hospitals for the isolation and characterization of major bacterial pathogens implicated in causing meningitis. CSF was collected from 201 patients and left over sample was used for the present study.

Laboratory Diagnosis
Left over CSF sample was transferred to the Department of Medical Laboratory sciences and kept in a deep freezer at minus 80°C until use. Each sample was then screened for CrAg using CrAg Lateral flow assay (Immuno-Mycologics Inc., Oklahoma, USA) as per the instruction of the manufacturer. The Lateral flow assay uses immunochromographic test strips that have been impregnated with monoclonal antibodies against capsular polysaccharide antigens common to fungi in the Cryptococcal species complex (C. neoformans and C. gattii). To perform the assay, 40 microliters of CSF was mixed with one drop of LF specimen Diluent (GLF025). Then the white end of a Cryptococcal Antigen Lateral Flow Test Strip (LFCR50) was submerged into the preparation and the result was read after 10 minutes at room temperature. The presence of two lines (test and control) on the test strip regardless of the intensity of the test line were interpreted as positive result, while the presence of a single control line was read as a negative result.

Ethical Clearance
All ethical considerations and obligations were duly addressed and the study was conducted after the approval of the Department Research and Ethical Review Committee (DRERC) of the Department of Medical Laboratory Sciences, College of Health Sciences, Addis Ababa University and the Addis Ababa City Health Bureau. Informed written consent was obtained from participants before data collection. The respondent was given the right to refuse to take part in the study and to withdraw at any time during the study period. Assent form was completed and signed by family member and/or adult guardian for participants under the age of 18 years.

Result and Discussion
With a declining incidence of AIDS-related cryptococcosis in the Highly Active Antiretroviral Therapy (HAART) era, and increasing use of immunesuppressive agents worldwide [21,22], non-HIV infected individuals (with or without predisposing factors) have become more frequently infected by the yeast. Ethiopia being a developing nation located in sub-Saharan Africa where anti-retroviral therapy is less available appears to fall into the category of regions with high prevalence of cryptococcosis. Furthermore, in contrast to immunecompromised patients, few reports have described the variety of C. neoformans, clinical presentation, cerebrospinal fluid (CSF) parameters and prognosis associated with cryptococcal infections among immunocompetent individuals [13]. To this effect, screening of crytpococcal infection in Ethiopian patients clinically diagnosed to have meningitis regardless of the immune status appears to be of a highest priority. Consequently, in the present study a total of 201 samples were collected from patients clinically diagnosed to have meningitis. Among study subjects, 106 (52.7%) were males and 96 (47.8%) were females. The ages of study subjects ranged from 1 day to 75 years with a mean age of 26 years. Of the total number of 201 patients 17 (8.5%) were positive for cryptococcal antigenemia of which 8 (4%) were male patients while 9 (4.5%) were female patients. As shown in table 1, the finding of the present study was comparable with the findings of previous studies conducted in Ethiopia with HIV infected patients [18][19][20] but much lower than similar studies conducted in AIDS patients in other sub-Saharan African countries [3,9,[23][24][25][26][27][28]. Index of suspicion, patient selection and intensity of evaluation, variation in test procedures and type of clinical sample used for detection and/or isolation and characterization the etiologic agent may have attributed to such a variation.  [29]. A total of 242 CSF samples collected from patients clinically suspected for cryptococcal meningitis were screened for Cryptococcus neoformans irrespective of their immune status. The result of the study depicted an overall prevalence of 8.3% cryptococcal meningitis and prevalence 16.6% cryptococcal meningitis among immunocompromised patients. The result of this study was in good agreement with our finding. Similarly, the prevalence of cryptococcis in apparently immunocompetent patients was conducted by Lui et al [13]. Out of 46 patients with Cryptococcosis, twenty patients (43.5%) were apparently immunocomptetent. The finding of Lui et al [13] is supported by the report of Pappas et al [30] that showed cryptococcosis in non-HIV patients of which 10-40% were immunocompetent. To determine the prevalence of cryptococcal infection, a retrospective analysis of 326 clinically diagnosed cases with meningitis over a period of five-and-a-half years was carried out by Prasad et al [31] of which fifty-four (16.6%) patients were found to have cryptococcal meningitis. Our finding was not in accordance with the findings of Prasad et al [31], which has demonstrated a higher prevalence of cryptococcal meningitis.
As a result of differences in exposure to the pathogen, cryptococcal meningitis is more frequently reported in men than women and rarely from children [4]. The finding of the present study in this regard was not in line with the findings of this study where the number of male and female patients with cryptococcal meningitis was more or less the same (8: 9).

Conclusion
Since clinical manifestations of cryptococcal meningitis are indistinguishable from other causes of central nervous system infection, all patients clinical diagnosed as having meningitis must be investigated for cryptococcal meningitis irrespective of their immune status. Furthermore, in view of the increasing number of infections, rapid, sensitive, and specific diagnosis of cryptococcal disease has become more important than ever in Ethiopian health institutions.

Limitation of the Study
Unable to perform other laboratory procedures as the result of inadequate clinical sample was the limitation of this work.