[COUNTRY STORY]

First-ever confirmation of visceral leishmaniasis and leishmaniasis species identification by PCR in Chad

Chad
Rapid outbreak response

Visceral leishmaniasis, also known as kala-azar, is one of the world's most deadly parasitic diseases, second only to malaria. An estimated 50 000 to 90 000 new cases of visceral leishmaniasis occur worldwide annually with only 25-45% reported to WHO. Left untreated, visceral leishmaniasis is fatal in over 95% of cases with an average of 538 deaths per year between 2016 and 2020 (ranging from 604 in 2016 to 347 in 2020) [1]. Visceral leishmaniasis is caused by a protozoan parasite of the genus Leishmania, transmitted to humans through the bite of infected sandflies.

Sporadic cases of visceral leishmaniasis were reported in Chad prior to 2018. Countries such as Sudan and Libya, which share borders with Chad, report thousands of cases each year. Between January 2018 and May 2021, an outbreak of visceral leishmaniasis was reported by three provinces in Chad – N’Djamena, Borkou, and Tibesti – resulting in 122 cases and six fatalities. In August 2020, there were rumours of a febrile illness decimating young gold miners in Tibesti and Borkou, hard-to-reach regions located in insecure areas partly controlled by self-defence militias. The suspected visceral leishmaniasis outbreak drew urgent attention to the need for intervention. Rapid public health action and WHO support aimed to strengthen surveillance, develop procedures for blood sample collection, storage and shipment, and laboratory testing of all suspected cases. By 2021, the outbreak was brought under control.

Photo Credit: © Mr Kaiwa Kaman Franklin

Photo Caption: Rugged terrain to reach those in need (about 1000 kilometres from the capital city of N’Djamena).

How did Chad do it, and how did the WHO Secretariat support Chad?

  • Investigation mission – The Ministry of Public Health and National Solidarity, with technical support of the WHO Country Office in Chad, deployed a mission to Borkou and Tibesti provinces. Nineteen blood samples were collected from patients demonstrating clinical signs and symptoms of visceral leishmaniasis. Environmental conditions were found to be suitable to sandfly vector development.
  • Polymerase chain reaction (PCR) analysis – The WHO Country Office financed the shipment of blood samples to the Laboratorio de Referencia e Investigación en Parasitología, Centro Nacional de Microbiología Instituto de Salud Carlos III, a WHO Collaborating Centre for Parasitology Research in Madrid, Spain. For each sample, a rapid Kr39 Antigen (Kr39 Ag RDT) and a polymerase chain reaction (PCR) test was performed. Among the 19 samples tested by PCR and 16 by Kr39 RDT, 13 were positive for the Leishmania donovanispecies of intracellular parasites. This was the first-ever confirmation by PCR of the existence of visceral leishmaniasis and identification of the species in Chad.
  • Monitoring and case management – The Ministry of Public Health and National Solidarity arranged weekly coordination meetings which brought together field actors and partners, in particular the WHO Country Office and the WHO Regional Office for Africa, to monitor the epidemiological situation and the management of cases to control the epidemic.
  • Deployment of medicines and diagnostics – A second joint WHO and Ministry of Public Health and National Solidarity mission made it possible to deploy medicines and rapid diagnostic tests in Borkou and Tibesti provinces and to strengthen the capacities of local service providers for the diagnosis and management of cases. Because the glucantime molecules (meglumine antimoniate) for the management of visceral leishmaniasis are expensive (more than 150 US dollars for a complete treatment) and often unavailable in Chad, WHO headquarters sent the molecules when they were needed.
  • Extension of investigations – A list of cases was created in the two epicentre provinces (Borkou and Tibesti), investigations were extended to other provinces, and cases were isolated in Ouaddaï (in northeast Chad) and N’Djamena, the capital city. A monthly report on the situation was prepared and shared with all partners.
  • Adoption of therapy protocol – Chad, with technical support from WHO and in line with WHO guidelines, provisionally adopted the dual therapy protocol (Sodium Stibogluconate-a pentavalent antimony derivative + Paromymocin) for 17 days of treatment. The adoption of this protocol enabled WHO to provide these two key molecules for management as well as rK39 RDTs for rapid diagnosis at peripheral level.
  • Training health care workers – Data on visceral leishmaniasis are scarce in Chad and not well known to health care practitioners. The Ministry of Public Health and National Solidarity and the WHO Country Office in Chad addressed this major challenge by training 30 service providers in case management in the two epicentre provinces, Borkou and Tibesti.

Although diagnosis of visceral leishmaniasis and the species identification have been made, the extent of the disease in Chad remains unknown and an enormous amount of work remains to be done. An epidemiological survey in all at-risk areas is being prepared with WHO Country Office support which will lead to further strengthening surveillance and control of the disease in Chad.

REFERENCE

[1] Weekly epidemiological record: Global leishmaniasis surveillance: 2019-2020, a baseline for the 2030 roadmap http://www.who.int/wer

Photo Credit: © Mr Kaiwa Kaman Franklin

Photo Caption: A mountainous trek during the trip to Bardai, epicenter of the epidemic.