April 9, 2019: Several cases of malaria have been confirmed in regions of Ecuador and Peru where the disease was once considered eliminated. New research by EPI investigator and medical geographer Sadie Ryan ties these cases to the collapse of Venezuela’s public health infrastructure and subsequent flow of emigrants through neighboring countries.
Malaria has been confirmed along a section of Ecuador and Peru’s shared border where the disease was declared eliminated by 2012. New published research by Emerging Pathogens Institute researcher Sadie Ryan documents seven cases between El Oro Province, Ecuador and the Tumbes Region of Peru, located along a well-traveled route actively used by migrants leaving Venezuela en route for South America’s southern cone.
“With the influx of migrant populations coming from Venezuela, people have brought complicated cases of malaria through,” says Ryan, who is also a medical geographer in UF’s geography department in the College of Liberal Arts and Sciences. “We know that these cases exist. But we don’t have enough surveillance in place anymore to catch it if it starts to establish locally.”
The governments of Peru and Ecuador made a massive push to eliminate malaria in this border region and declared their campaigns successful between 2011 and 2012. But then they scaled back surveillance efforts when international funding for malaria was cut, such as the network of community health volunteers and surveillance of Anopheles mosquitoes. Although the public health sector continues to test around 20,000 people for malaria per year in the city of Machala alone, resource limitations increase the risk of a malaria outbreak.
Eliminating mosquito-borne diseases is a tricky business. Especially when a disease such as malaria is established in the regions surrounding an elimination area. “What we tend to see in areas that declare elimination of a vector-borne disease, is that unless they keep up surveillance activities, the diseases can become reestablished,” Ryan says. However, these newly documented cases do not mean that malaria has become re-established in these borderlands. Rather, they raise alarm bells that the disease could switch from being “eliminated” back to being transmitted locally.
Ryan cautions that her latest research focuses on just a small part of Ecuador and northern Peru, and that there are likely more cases that are going undiagnosed and unreported. “This is a call to arms for starting surveillance and paying attention,” Ryan says. “There is an unstoppable wave of migrants coming through these areas, and the governments need to be prepared. There will be diseases coming through, it’s more a matter of how they will be dealt with, or not.”
Some malaria cases can become complicated. If initial treatments do not clear the parasites from a person’s body, they may re-emerge and require follow-up care. Relapses are often more difficult to treat compared to an initial infection. But this sort of follow-up care can be challenging, or impossible, to provide for a migrating population.
“We need to be vigilant for potential complicated cases of malaria that need follow-up care,” Ryan says. “Global aid groups also need to rethink humanitarian aid packages in terms of rapidly mobilizing malaria medicines to these areas that probably don’t have them, because they’d been declared malaria free.”
EPI director Glenn Morris, and EPI researchers John Lednicky and Gabriela Blohm, recently coauthored a separate study published in The Lancet Infectious Diseases that documents increasing rates of insect-borne diseases in Venezuela as the country experiences political and social collapse. Their research predicted public health threats to surounding countries, which Ryan's study has now captured a specific example of. Below, they discuss the challenges of local malaria elimination, and detection and treatment within a migrating population.
Morris is an editor of the CDC's journal, Emerging Infectious Diseases, where Ryan's paper published. Lednicky is an EPI investigator and research professor in UF’s College of Public Health and Health Professions department of environmental and global health; he oversees postdoctoral researcher Blohm, who is a Venezuelan citizen and is also affiliated with the EPI.
Q: What are your initial thoughts on seeing a new paper documenting malaria along a route used by migrants leaving Venezuela, and that this disease is now popping up in an area where it was previously eliminated seven to eight years ago?
Morris: The Ryan paper further reinforces the findings in the original Lancet paper. The Lancet paper provided an overview of problems related to vector-borne diseases in Venezuela, and noted the risks associated with cross-border transmission. The Ryan paper provides a very specific example of this, related to malaria cases in Ecuador and Peru.
Blohm: I am deeply saddened by these findings. Venezuela was once leading Latin America’s efforts to eliminate malaria. However, I have to add that I am not surprised by these findings. Throughout our work in Venezuela, we have been witnessing a catastrophic collapse in public health infrastructure, mosquito control, and access to antimalarial drugs. It is heartbreaking but not surprising that Venezuelan migrants would be entering other countries with malaria and other diseases that were previously under better control.
Lednicky: None of this is surprising. Most of the cases in the report were in Venezuelans who harbored one of the parasites that cause malaria. The few autochthonous cases suggest reintroduction into areas previously cleared of the parasite. When a disease gets eradicated, complacency is common among the population and public health providers. One reason this happens is people tend to have short-term memories. As the economy collapses, the authorities in Venezuela do not prioritize spending on preventive public health measures, and this has allowed the vectors of malaria to once again proliferate.
Q: It’s not surprising that malaria was confirmed in Venezuelan emigrants. But is it significant that Dr. Ryan’s paper documents cases of autochthonous malaria, spread from one individual and acquired by another in the same place, along the Ecuador–Peru border which was previously malaria free?
Morris: A great deal of effort has been expended by health departments at the country level – and at the international level – to control and eliminate malaria – i.e., to be able to declare some or all of a country “malaria free.” In this instance, apparent introduction of the disease into a previously malaria-free region by refugees from Venezuela is a big deal – and has the potential for undoing all the effort that went into making a region malaria free. This gets back to the idea that public health is dependent on everyone doing their part – if one country has increasing problems with malaria, and is spreading the infection beyond its borders, it can create major problems for other countries that have been successful with control effort.
Blohm: I agree that it is not surprising. The fact that this region was previously malaria-free does not mean that malaria cannot become re-established. These findings suggest to me that the vectors are still present in this region.
Lednicky: It is worrisome that autochthonous spread is now occurring in surrounding countries, and one needs to look at the response from these other countries. Have they also reduced or stopped malaria control measures? Are they also complacent about malaria? Were they caught off-guard because they too had dropped the ball regarding malaria control? Does this point to a misuse of resources?
Q: What can public health officials in neighboring countries do to prevent the occurrence or spread of malaria, and other vector-borne diseases, given that the high-volume of people displaced may continue for some time?
Morris: They need to maintain heightened surveillance for malaria and other vector-borne diseases, to try to identify and “contain” any cases that may enter the country – this includes provision of treatment, to reduce the risk of spread, enhanced mosquito control efforts, and, as noted, heightened surveillance.
Blohm: Increased surveillance is a must. Laboratory-confirmed clinical diagnosis is important for tracking and controlling the spread of malaria to other countries.
Lednicky: This is not a question that can be easily answered. Effective mosquito spraying, and other techniques, to control arthropod vectors should be engaged in. But some of the agents that cause arthropod-borne diseases have non-human hosts, so it is possible that they get reintroduced into the local fauna which then serve as reservoirs of the infectious agent. Moreover, some of the agents (like Zika virus) can be spread through sexual transmission. It would not be practical to quarantine all newcomers, and test them for all possible agents, especially as Venezuela has many arthropod-borne viruses that may not be common in other countries. Moreover, Venezuela is a geographically and ecologically diverse country… and along with that diversity come different infectious agents. It would be impractical/impossible to test for all agents.
Q: What are your thoughts on whether elimination of malaria is possible in South America? Is “elimination” really just local eradication, or is it possible to eliminate malaria on an entire continent?
Morris: Tough question. Globally, there are groups that think that elimination of malaria is possible – but it is going to be difficult, particularly in Africa. At a continental level – malaria transmission used to occur in the U.S. (my mother remembers taking weekly quinine in south Mississippi to prevent malaria), but local transmission has been eliminated. Malaria has also been eliminated in much of South America. However, “hot spots” remain, such as Haiti in the Caribbean. As long as the disease remains active in at least some parts of a continent, there is always the possibility that it will be reintroduced into areas where elimination has been successful.
Blohm: I believe that it is possible to eliminate malaria in South America. Venezuela came close to eliminating malaria several decades ago. I think that elimination will require local eradication.
Lednicky: Malaria can be controlled but it is doubtful if it can be totally eliminated in tropical countries. What is needed in the region are medications to combat malaria, and chemical sprays and treatments that can be used to kill the mosquitoes that transmit the parasites.
Q: Is there anything else you’d like readers to know about malaria in South America, or about the continent-wide public health risks from arboviruses poised by Venezuela’s collapse?
Morris: For me – the main point is that public health requires a global effort – and, in particular, no matter how hard a country works to enhance public health, you want neighboring countries that have a similar public health commitment. The breakdown of the public health infrastructure in Venezuela is creating problems in neighboring countries, and will continue to create problems until the internal issues in Venezuela are resolved.
Blohm: I would like readers to support the delivery of humanitarian aid and equipment for laboratory diagnosis of these diseases in Venezuela. Without adequate surveillance, it is really difficult to provide accurate diagnoses to patients. Without laboratory confirmation, it is also very difficult to know how to intervene and prevent further spread.
Lednicky: One should consider the risks posed by other pathogens also. Measles virus, for example, used to be the virus that killed the most children that died of virus infections in the last two centuries. What is happening in the areas surrounding Venezuela is happening in many other places, but this has been overlooked by the world. For example, fighting in Africa has caused displacement of populations and the spillover of diseases; but the world has paid little attention.
Malaria is caused by several species of parasites from the Plasmodium genus. The parasites get injected into a person’s bloodstream through a mosquito’s syringe-like proboscis when the insect bites. Ryan’s research found six cases of malaria caused by P. vivax and one case caused by P. falciparum, which causes the most deadly type of malaria. Watch this PBS video to learn how mosquitos bite without us noticing, probe for a blood vessel, and make the most of their meal.
Written by DeLene Beeland; Graphics: (Top photo) Plasmodium falciparum trophozoites in a blood smear, CDC Public Health Image Libarary; (Map) Route of Venezuelan emigrants, courtesy of Sadie Ryan; (Video) by PBS.