The World Health Organization (WHO) is shifting its focus toward active screening of girls and women of childbearing age to detect the presence of Trypanosoma cruzi, the causative parasite of Chagas disease. Recent evidence1,2 demonstrates that diagnosing and treating women of this age group before pregnancy can effectively prevent congenital transmission.
“Identifying pregnant women already infected with the parasite, as well as newborns and siblings, has been a major challenge in both endemic and non-endemic countries” said Dr. Pedro Albajar Viñas, medical officer, WHO Department of Control of Neglected Tropical Diseases. “With the progressive control of transmission by vectors and through blood transfusion, updating, reinforcing and expanding standardized screening measures for congenital transmission make absolute sense.”
Up to now, control and prevention strategies for Chagas disease largely relied on the early detection and treatment of infected newborns and siblings of pregnant women. But a recent shift in approaches to prevent transmission globally – including in non-endemic countries – is through active, systematic screening of girls and women at risk of infection and provides excellent opportunities for prevention of posterior transmission throughout pregnancy and birth.
“There are several instruments through which detection can be done and these can be complemented in combination with biomedical and psychosocial strategies,” said Dr. Manuel Segovia, director of the Regional Unit of Tropical Medicine, Hospital Clínico Universitario Virgen de la Arrixaca, Murcia, Spain. “Once infection is confirmed in a patient, physical and complementary examinations are needed to determine the clinical presentation of the disease,” Segovia added.
Generally, it is estimated that under-diagnosis of Chagas disease cases is as high as 90 percent, with under-diagnosis of congenital transmission believed to be even higher. This constitutes the most frequent means of transmission, especially in areas where infection through insect vectors is not transmitted and where transmission through blood transfusion has been interrupted.
Accelerating the elimination of congenital transmission will mean implementing strategies and methods to detect, screen and diagnose all infected pregnant women as well as infected newborns and their siblings and to treat them as soon as possible.
It will also imply implementing similar strategies for all women of childbearing age, ideally at paediatric age (under 19 years old ) when the effectiveness of antiparasitic treatment is confirmed much more frequently and rapidly than in adults and with fewer adverse reactions.
““Implementing universal screening programmes requires appropriate laboratory protocols that, according to availability, should include old and new diagnostic tests, such as standardized and validated chemiluminescence,” said Dr. Amadeo Sáez-Alquezar, National Programme of Quality Control, Brazilian Society of Clinical Analysis. “This also implies building capacity and assessing the costs of implementation of screening and diagnosis as well as the necessary follow-up of patients.”
It will also be important to set up internal and external quality control of laboratories in order to optimize the laboratory protocols for screening and diagnosis with the available commercialized tests and permit the verification of interruption of transmission.
The details were discussed during an international technical meeting convened by WHO at the Clinical University Hospital of Virgen de la Arrixaca in Murcia, Spain on 9–10 October 2018.
Experts attending the Second WHO Technical Consultation on the Control of Congenital Chagas disease in non-endemic countries also analysed the need to improve information and surveillance systems on congenital Chagas disease by notifying all cases, which can definitely help in measuring coverage and verifying the interruption of transmission.
The meeting was organized in collaboration with National Centre of Tropical Medicine, Health Institute Carlos III of Spain and the Regional Centre of Tropical Medicine, Clinical University Hospital of Virgen de la Arrixaca.
The global strategy to eliminate Chagas disease is supported by the donation to WHO of the two available and alternative antiparasitic medicines for treatment of Trypanosoma cruzi infection, which leads to Chagas disease.
Nifurtimox, donated by Bayer, has been distributed free of charge for patients of all ages since 2008. Benznidazole, donated by Insud Pharma, will be distributed freely to treat patients aged under 19 years.
Chagas disease is found mainly in endemic areas of 21 Latin American countries5 where infection is transmitted mostly by vectors to humans by contact with faeces or urine of triatomine bugs (known as “kissing bugs,” among many other popular names).
For centuries, the disease was strictly a Latin American disease of rural populations, but movement of people from rural to urban areas and to other continents, despite significant advances in vectorial control, has expanded the reach of disease transmission channels towards non vectorial routes, such as blood transfusion, congenital transmission and organ transplants.
Chagas disease has been detected in the United States of America, Canada and in many European and some Western Pacific countries due mainly to migration. However, cases of infection have been reported among travellers returning from Latin America and even in adopted children.
About 6 million to 7 million people worldwide are estimated to be infected with Trypanosoma cruzi, the parasite that causes Chagas disease. There is no vaccine against Chagas disease. Domiciliary vectorial control and transfusional control, together with congenital transmission, remain the most effective methods of preventing transmission in Latin America.
Chagas disease was named after Carlos Ribeiro Justiniano Chagas, a Brazilian physician and researcher who discovered the disease in 1909.