Parasitic Diseases of the Central Nervous System: Treatment and Control
This article is the third in a 3-part series on parasitic diseases of the central nervous system (CNS) and it highlights some of the treatment advances that are available for patients with these diseases, as well as disease control strategies that have been implemented by the World Health Organization (WHO) and other partners.
This article, based on a recent publication by Arturo Carpio, MD, Universidad de Cuenca, Ecuador, and colleagues, is the third in a 3-part series on parasitic diseases of the central nervous system (CNS). It will highlight some of the treatment advances that are available for patients with these diseases, as well as disease control strategies that have been implemented by the World Health Organization (WHO) and other partners.
Recent Advances in Treatment
Management of parasitic infections of the CNS can involve medical and surgical treatments that may be used to eradicate the parasite and treat secondary complications that arise from its presence.
Antiparasitic drugs are used for most infections. However, clinicians may choose to avoid them in certain cases, such as when the risks of treatment outweigh the potential benefits.
The efficacy of antiparasitic drugs varies. In particular, these agents may be ineffective if the parasite is already dead but still causing symptoms, as occurs with calcified cysticercosis lesions in the CNS.
However, progress has been made in the treatment of some CNS parasitic infections.
For example, the authors note that in a recent study in patients with cysticercosis with active cysts in the brain, combination albendazole plus praziquantel was significantly more effective than albendazole monotherapy in eradicating the parasite in individuals with 3 or more active cysts; however, combination therapy did not significantly influence complete seizure remission in these patients.
Significant advances have also been made in the treatment of the second, meningoencephalitic stage of Trypanosoma brucei gambiense (human African trypanosomiasis [HAT]). Treatment of this condition has typically involved the use of highly toxic agents such as melarsoprol, which is associated with reactive meningoencephalopathy and treatment-related death. However, nifurtimox—eflornithine combination therapy (NECT)—which consists of intravenous (IV) nifurtimox therapy for 10 days and IV eflornithine therapy for 7 days—is now on the WHO Essential Medicines List.
Indeed, the authors note that findings from a recent retrospective cohort study of patients treated with NECT in a ‘real world’ setting in the Democratic Republic of the Congo confirmed efficacy and safety data obtained from clinical trials. In particular, treatment with NECT resulted in high cure rates, very low rates of in-hospital mortality, and low rates of major adverse events. Compared with adults, children tolerated NECT better and experienced fewer adverse events.
Unfortunately, NECT is unlikely to be effective against second-stage Trypanosoma brucei rhodesiense HAT, and regimens involving melarsoprol remain the only effective treatment option. However, advances in treatment regimens have decreased the safety concerns associated with this agent. The authors note that in one recent study in particular, a 10-day melarsoprol-only regimen resulted in an incidence of encephalopathic syndrome and case fatality rate that were similar to those previously reported in association with traditional therapy (which typically involves suramin pretreatment followed by multiple melarsoprol infusions and hospitalization for 1 month). Parasitic and clinical cure rates were high, and mean hospitalization time was reduced to 13 days. This new regimen is now preferred for treating second-stage Trypanosoma brucei rhodesiense HAT.
Research is ongoing to develop safe and effective treatments for patients with CNS parasitic infections. Some new drugs are already in the pipeline, such as fexinidazole for the treatment of CNS infections due to Trypanosoma cruzi and Trypanosoma brucei rhodesiense.
In contrast, although the drugs for treatment of CNS malaria infection are effective, their use is associated with high mortality, so research has focused on improving adjunctive care to reduce mortality.
Prevention and Control
Ultimately, prevention and control of parasitic infections that affect the CNS are critical to progress towards eradicating these diseases.
Indeed, many large-scale programs for the control, elimination, or eradication of NTDs, including those due to parasites that infect the CNS, are being implemented by the WHO and other organizations.
In particular, expansion of malaria control programs has helped to reduce the incidence of malaria by 30% worldwide and by 34% in Africa. These programs have included strategies such as vector control (by the use of insecticide-treated mosquito nets and indoor residual spraying), public awareness strategies, disease treatment, and seasonal chemoprevention.
Similarly, many countries, such as China, have implemented schistosomiasis control programs that have interrupted disease transmission in most endemic areas. These programs have included strategies such as dam construction, delivery of drinking water, and provision of basic sanitation.
Consequently, the authors stress that “[o]vercoming parasite-related disease makes sense both for economies and for development,” in particular because if their burden is not significantly reduced, other goals (including those in education, gender equality, poverty reduction, and economic growth, and other areas of health) will be difficult to achieve.
“By tackling parasitic diseases, more than one billion people living in low-income endemic areas have a chance for improved health and wellbeing. These diseases should be neglected no more,” they conclude.
Read the first and second articles in the series here:
Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.