Neuroinfectious diseases are infections affecting the central and peripheral nervous system, possibly due to bacterial, viral, fungal, or parasitic infections1. The route of infection to the nervous system could be through direct inoculation, blood circulation, retrograde spread, or others2. Central nervous system infections are often challenging to diagnose, and the burden of undiagnosed nervous system infections is currently underreported; despite the recent advances in investigative technology, about 30% of patients with suspected central nervous system infections never received an etiological diagnosis, with nearly one-third of these patients dying of the illness3,4. Neurological disorders related to neuroinfectious diseases are highly prevalent in sub-Saharan Africa, which constitute a significant cause of disabilities and economic burden for the patients and society5. There are dual burdens of neuroinfectious diseases in developing countries of Africa in which the conditions are both under-recognized and under-treated6. One of the significant challenges of neuroinfectious diseases in Africa is the lack of neurological experts, with the average number of neurologists to the general population of about 1–3.4 million in some African countries; with about 11 countries not having any neurologists, the case is worst in neurological surgery6,7.
Epidemiology of neuroinfectious diseases
There are few pieces of literature reporting the epidemiology of neuro-infectious diseases in Africa. Still, with a global incidence of about 389/100,000 estimated between 1990 and 2016, certain infections have been noted to affect the nervous system8. The infectious diseases of the nervous can be grouped according to their causative agents, such as bacterial, viral, fungal, and parasitic.
- Common bacterial infections of the nervous system
- Bacterial meningitis has been reported to be prevalent in some regions of Africa, especially sub-Saharan Africa, which is referred to as the meningitis belt9–12. About 393,614 cases of bacterial meningitis were reported by the World Health Organization in Nigeria between 1991 and 201113. The commonly indicated organisms causing bacterial meningitis include Streptococcus pneumonia, Neisseria meningitidis, Listeria monocytogenes, Haemophilus influenza, and Mycobacterium tuberculosis14. Another important bacterial infection of the nervous system that has been found to be epidemic in Africa is neurosyphilis which accounts for about 3% of all bacterial neuro infections reported in Africa15.
- Common viral infections of the nervous system
- Some of the infections of the nervous system are of viral origin, which causes severe morbidity and mortality in Africa, as many potentially lethal neurotrophic viruses were discovered in Africa9. Some emerging viral infections in Africa, such as West Nile virus, Ebola virus, Chikungunya virus, and Zika virus, were found cause some neurological sequelae such as encephalitis, hydrocephalus, and meningitis; these were found to be endemic in some regions of sub-Saharan Africa with increasing incidence16–22. other viral infections such as herpes simplex, varicella zoster, cytomegalovirus, Epstein Barr, and HIV are endemic in some areas of Africa23.
- Common fungal infections of the nervous system
- Cryptococcal meningitis is one of the leading causes of meningitis globally. It was reported in 2017 that about 160,000 people in Africa had been diagnosed with cryptococcal meningitis, with 98% localized to sub-Saharan Africa24. Countries like Nigeria, South Africa, and Mozambique have an average of 20,000 cases of cytomegalovirus per year, with North Africa recording the least cases24. Despite the recent decrease in the yearly incidence of cryptococcal meningitis, the mortality of cryptococcal meningitis in Africa is about 44% on short-term follow-up and about 73% on long-term follow-up25–30. Other nervous system fungal infections, such as candida and Histoplasma, have also been reported in Africa31.
- Common parasitic infections of the nervous system
- Cerebral malaria affects about 3 million children worldwide, accounting for about 1 million death, with 90% occurring in Africa32. There has been a recent decline in the incidence of cerebral malaria by up to 50% in some countries like Tanzania, Kenya, and Zambia33–35. Neurocysticercosis is the most common parasitic infection of the central nervous system globally, which is found to be endemic in low-income countries of Africa36,37. Neurocysticercosis accounts for a significant cause of seizures and epilepsy in Africa37–39. Human African Trypanosomiasis is found to be endemic in Africa, with a prevalence of about 50,000–70,000 and an annual incidence of about 17,000. Still, in endemic countries, it causes some significant neurological sequelae40,41. Toxoplasmosis is another parasitic infection of the nervous system that is of public health importance in Africa, with prevalence varying by geographical distribution. However, Toxoplasma gondii was widely distributed in Mali and other west African countries42,43.
Factors influencing the outcome of neuroinfectious diseases in Africa
Predisposing factors to neuroinfectious diseases
Some factors have been identified to contribute to the prevalence of neuroinfectious diseases in Africa, which include poor sanitation, nutrition, inadequate infection prevention control programs, environmental conditions favoring the endemicity of some infections, inadequate immunization programs, and others44–49. The increase prevalence of HIV infection was also found to be associated with the increased prevalence of viral meningitis in Africa, the environmental conditions, such as high temperatures, were found to contribute to the endemicity of meningococcal infections in the meningitis belt of sub-Saharan Africa50.
Challenges of management of neuroinfectious diseases
Management of neuroinfectious diseases in Africa has been faced with several challenges part of in which includes a lack of access to adequate healthcare especially neurological care, access to diagnostic facilities, and limitations in the availability, number, and geographical distribution of trained specialists51–53. Another challenge is people in Africa tend to access traditional health practices with an average of conventional health practitioners to the general population of about 5:1000, while for neurologists is 1: 1,500,000–1: 5,000,000 and neurosurgeons 1:4,000,000–1: 6,000,00054–56.
The study noted several bacterial, fungal, viral, and parasitic diseases that significantly affect the occurrence of neuroinfectious diseases. On the African continent, the prevalence of neuroinfectious illnesses has been rising over time, with a heavy burden on low and middle-income countries57. Its management in the area is faced with some difficulties, including inadequate care, poverty, research, and an unstable health care system.
The majority of neuroinfectious illnesses necessitate accurate diagnosis and care. To properly diagnose these infections and treat the sickness, it is necessary to ascertain the nature of the infection. A correct diagnosis is necessary to identify the type of parasite affecting the nervous system in cases of parasitic diseases like malaria. In addition, a solid health care system will offer the range of people and physical resources required to combat different neuroinfectious illnesses. These include human resources like medical professionals and Infrastructural resources like medical labs, hospitals, and cutting-edge health care facilities. They are necessary because they would make a significant contribution to overcoming the numerous obstacles to the detection and treatment of neuroinfectious illnesses58.
Governments and stakeholders in low and middle-income countries should offer health care delivery subsidies to solve the problems brought on by poverty; this would enable free treatment to the needy and disadvantaged while also expanding the reach of health care delivery in these areas.
Finally, there is a need for proper research on various infections affecting the nervous system. Ngarka et al5 study on neuroinfections in Africa demonstrated the need for a thorough investigation into the risk factors, triggering factors, and mechanisms underlying these infections. This would aid in the development of novel therapeutic approaches for the effective management of these infections5.
Neuroinfectious diseases are often underreported in Africa. Public health stakeholders in the continent must pay key attention to the growing prevalence of neuroinfectious diseases.
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