Malaria on the decline in Mexico

Malaria resistance problems to drugs are ruled out. World Malaria Day is commemorated on April 25. Africa accounted for 95 percent of cases and 96 percent of deaths.

Malaria on the decline in Mexico
Drop in the incidence of malaria in Mexico. Photo: UNAM

According to the Ministry of Health of the federal government, in the last decade, 24 states have not registered autochthonous cases and could be certified as malaria-free areas, including Aguascalientes, Baja California, Baja California Sur, Mexico City, Coahuila, Colima, Durango and the State of Mexico.

Nayarit, Tabasco, and Quintana Roo have also had no reports in the last three years, but remain hotspots of residual transmission. Four more - Campeche, Chiapas, Chihuahua and Sinaloa - have active transmission.

It is estimated that in 2020 the number of deaths worldwide due to this disease was 627,000, 95 percent of the cases and 96 percent of the deaths were concentrated in Africa, of which 80 percent corresponded to children under five years of age, according to the World Health Organization (WHO).

For the last decade, in Mexico they have decreased due to the strategies adopted by the health authorities, explains Lorena Gonzalez Lopez, an academic from the Department of Microbiology and Parasitology of the School of Medicine (FM).

Despite the health crisis caused by COVID-19, "we are on the right track, it is optimistic to see that the cases of this disease have been reduced and that we are on the way to its elimination". The expert mentions that in 2021, less than 200 cases were reported in the country. "In fact, for several years the trend has been that way and it has been reducing, which is quite important".

Meanwhile, in the world scenario, as of 2020 there was a slight increase in the incidence and deaths from this cause, which may be due to two important factors: strategies were not fully implemented due to the pandemic, and the WHO generated new algorithms and forms or strategies for its identification.

On the occasion of World Malaria Day, which is commemorated on April 25, the expert emphasizes that we also do not have problems of parasite resistance to antimalarial drugs, one of the problems that occur significantly in other countries. Since 2007, every April 25, the member states of the WHO commemorate this event with the global commitment to eliminate the disease based on efforts and concrete prevention actions.

Malaria depends on mobility

Malaria is a disorder -preventable and curable, but it can be fatal- caused by parasites that are transmitted to humans by the bite of infected female mosquitoes of the Anopheles genus.

It is an infection caused by a parasite of the Plasmodium genus, of which five species affect humans; one of them, Plasmodium falciparum, the most lethal if not treated in time, is found mainly in Africa and some South American countries.

In the case of Mexico, according to the epidemiological bulletin, in 2009 approximately 2,595 people were reported infected by Plasmodium vivax, the most frequent in Mexico and widely distributed in the world, causing malaria in its not so virulent or lethal form.

The disease is not necessarily associated with poverty and depends on human mobility and migration, an important factor in Mexico for its control.

Unlike other vectors such as Aedes aegypti, the main species responsible for Zika, dengue, and chikungunya, Anopheles has particularities such as reproducing in cleaner and more oxygenated water, although some species also reproduce in water with more organic matter. "It is a more delicate mosquito, but with a good strategy to spread".

Symptomatology is varied -according to the vector and the parasite's life cycle-, such as a fever that reaches 41°C, followed by profuse sweating, and finally chills and extreme tiredness, manifestations that are repeated every two or three days and have a duration of two to three hours. Affected people feel extreme tiredness, symptoms that are also repeated every two or three days, which is somewhat exhausting.

Those affected may present anemia, yellow pigmentation of the skin (jaundice), and probable enlargement of the spleen and liver (splenomegaly).

In the case of Plasmodium vivax, at some point, its symptoms diminish or infected persons do not develop any symptoms at all. However, there could be relapses years or months later, depending on the parasite's life cycle. "The parasite remains 'asleep' in the liver and suddenly there is no major problem, but after a certain time, mainly due to decreases in the immune response of individuals, it reactivates and the disease invades the red blood cells again and the symptoms reappear".

This disease is incapacitating, which represents economic losses because most of the patients are of working age; fever and extreme tiredness prevent them from working, "this is one of the main consequences in the country".

Against itself

There will always be mosquitoes and several of them will also be vectors or transmitters of some disease and that, like bacteria, create defense mechanisms against insecticides and other control methods. "Therefore, many of us have turned to the study of arthropods to try to understand them, the goal is that there will be no more people affected by malaria".

For some years now, the academic from the School of Medicine and her colleagues have been analyzing the replication cycle inside red blood cells (the study of molecules or proteins related to this process). In a second instance, they are studying the effect of the Plasmodium berghei parasite on the mosquito's immune system and its development inside the insect, all aimed at finding strategies for its elimination through the mosquito itself.

This team has collaborated with other research centers, such as the University of California, Irvine. The aim is to generate genetically modified organisms to interrupt the transmission cycles of malaria and other diseases caused by these vectors. Progress in malaria control is encouraging because we could be talking about the complete elimination of a parasite that has killed, and continues to kill, thousands of people in the world.

The first vaccine approved

The vaccine against malaria recently approved by the WHO is a milestone and the first one against a parasitic disease; it represents a great advance for the world of parasitology, as it took more than 30 years of research to obtain it.

Immunization, plus the use of mosquito nets, fumigation, analysis and treatment of patients, as well as taking pertinent measures in case of traveling to areas with higher risk and carrying out preventive treatments with a medical prescription, must go hand in hand for greater success in its combat, especially in children.

In December 2021, Mexico signed the E-25 initiative, promoted by the WHO to achieve the elimination of the malaria epidemic by 2025.