Dozens of plastic boxes stacked to the ceiling in a climate-controlled room in a new wing of the Butantan Institute’s vivarium are home to about 5,000 live specimens of Tityus serrulatus, the yellow scorpion, the species that causes most human poisonings in Brazil. Technicians and researchers from the arthropod laboratory move carefully, but fearlessly, among the boxes to feed these creatures some cockroaches and crickets, which are taken each day from a supply of thousands of insects kept in the adjoining rooms.
Scorpions—both yellow and other species—are kept at Butantan for two purposes. The first is to produce the serum used to neutralize the action of the poison, which has become increasingly important in view of the almost 600% increase in the number of accidents and deaths caused by these insects in the last 15 years. This increase is the result of urban expansion into areas once covered by forests, the accumulation of garbage and debris that attract insects in search of food, and the ability of these creatures to adapt to varied environments, from humid forests to the dryness of deserts. According to statistics from the Ministry of Health, scorpions caused the most accidents involving poisonous animals in Brazil, with 74,598 cases recorded, and caused more deaths (119) that snakes (107) in 2015 (see chart).
The second purpose is to investigate the effects—often unanticipated—of scorpion venom on the human organism. “Knowledge of the poison’s components and their effects still has many gaps,” says Dr. Fan Hui Wen, Butantan’s project manager, who oversees the production of the serum used to combat scorpion stings. “Some species are causing accidents with clinical manifestations different from those of the past.”
In a study published in the September 2016 issue of the journal Toxicon, researchers at the Manaus Tropical Medicine Foundation presented perhaps the first recorded case of an accident classified as serious that included muscle spasms and neurological disorders caused by Tityus silvestris, a scorpion species common in the Amazon and generally associated with non-serious accidents. A 39-year-old man with liver disease caused by hepatitis B, and who was awaiting a liver transplant, was stung on the elbow and shoulder while asleep at his home on the outskirts of the city of Manaus in northwest Brazil. Three hours later, he arrived at the Tropical Medicine Foundation hospital reporting only pain and paresthesia (tingling) in the stung area on the left arm.
Within two hours, however, the man had difficulty breathing, tachycardia, hypertension and muscle spasms. His clinical picture worsened. He was admitted to an intensive care unit, received serum and other medications, and was released just seven days later. “This case indicates that the clinical picture can become complicated regardless of the species that causes the poisoning,” says biochemical pharmacist Wuelton Marcelo Monteiro, a researcher at the Foundation and one of those responsible for the study. “There are still few studies on the consequences and varied effects of this species, which is geographically distributed over a wide area of the Amazon.”
Among the approximately 160 scorpion species found in Brazil, only 10 are poisonous to humans. In general, the poison, which is made up of proteins, enzymes, lipids, fatty acids and salts, acts on the nervous system, causing intense pain and muscle numbness at the site of the sting. Less frequently, systemic effects such as vomiting, tachycardia, hypertension, intense sweating, agitation and drowsiness are seen. Difficulty breathing is characteristic of the most serious cases, seen mainly in children. Stings by Tityus obscurus, which are common in the Amazon region, can also cause neurological effects, such as spasms, tremors and an electric shock sensation. “Since the scorpion venom can be rapidly absorbed into the bloodstream,” says pediatrician Fabio Bucaretchi, a professor at the University of Campinas School of Medical Sciences (FCM-Unicamp), “the clinical manifestations indicative of serious poisoning generally begin during the first two hours after the sting.”
In a major study published in 2014 in Toxicon, Bucaretchi and other researchers examined 1,327 cases of scorpion accidents treated at Unicamp’s Hospital das Clínicas between 1994 and 2011. They found that the most frequent accidents resulted in only local reactions (79.6%), while systemic reactions with vomiting, sweating and changes in heart rate were less common (15.1%). The so-called dry sting—no signs of poisoning—accounted for 3.4% of all the cases analyzed, while the most serious life-threatening cases represented 1.8%. “All serious cases and the only lethal case occurred in children under the age of 15,” says Bucaretchi.
Most accidents identified as caused by insects were attributed to the black scorpion, Tityus bahiensis (27.7%), and to the yellow scorpion (19.5%), usually the main cause of accidents and, in this study, responsible for the most serious occurrences. The yellow scorpion is also worrisome because of its ability to adapt to the urban environment and for the way it reproduces. Females of this species can reproduce by themselves, without the need for males, through a process known as parthenogenesis; each brood can result in as many as 30 young scorpions.
In the laboratory
“Studies of the Tityus serrulatus venom help us to get a clinical picture of how the poison works in the body, direct the production of better antivenoms and enable discoveries of new drug therapies,” says biomedical scientist Manuela Berto Pucca, who in July 2016 was contracted as a professor by the School of Medicine of the Federal University of Roraima (UFRR).
For her postdoctorate at the Riberão Preto School of Pharmaceutical Sciences of the University of São Paulo (FCF-RP-USP), she isolated two toxins, called Ts6 and Ts15, from the yellow scorpion venom. In vitro tests of the two toxins showed that they inhibited both proliferation of a group of white blood cells, the T lymphocytes and the production of a cytokine—a communication molecule of the immune system—known as interferon-gamma. According to Pucca’s study, published in the February 2016 issue of the journal Immunology, this property could qualify the two toxins as candidates for drugs against autoimmune diseases. “Testing has already begun and it looks promising,” she says.
Under the supervision of Dr. José Elpidio Barbosa, a professor at USP’s Ribeirão Preto School of Medicine (FM-RP), Pucca developed a human monoclonal antibody (produced using DNA cloning techniques) that stopped the action of the yellow scorpion venom in tests on cells and animal models (mice). Based on the results, the researchers suggested using the antibody as an alternative to the serum currently used against scorpion stings. But she notes that one of the main limitations of the new antibody is the cost of production, estimated at R$3,000 per ampoule.
“We want to improve the antidote, but we are also looking for new drugs that may come from molecules isolated from the venom,” says chemist Fernanda Portaro, a Butantan researcher. She and her team and colleagues from other Institute laboratories have isolated and are characterizing two compounds extracted from the venom: one with pro-inflammatory action and another with analgesic activity. “Scorpion venom works like an orchestra performing a symphony, in which each element has a specific function, targeting either the muscles, the nervous system or the heart,” says biologist Daniela Carvalho, a member of Portaro’s team.
An estimated 2.5 billion people in the world live in areas where scorpion stings are a threat, and there are 1.2 million poisoning cases annually, with 3,500 deaths, caused mainly by delays in seeking medical attention. “Fatalities can be avoided when medical help is sought immediately, and treatment begins shortly after the accident,” Butantan’s Dr. Wen advises.
After a tour of the scorpion rooms, Pucca showed off another room where the manual extraction takes place. Each insect receives a low-intensity electric shock on its tail and, in response, releases a small whitish droplet of venom. A large population of scorpions must be maintained because the insects cannot withstand more than five extractions induced by electric shock, says Denise Candido, the biologist responsible for extracting scorpion venom.
The insects come from hospitals (people usually take them there for purposes of identification after being stung), zoonotic control centers or from the researchers’ own expeditions, and they enter the production line only after being quarantined, which eliminates those that may carry diseases. Later the sera are produced by the same method used against snake and spider bites: the venom is diluted and administered to horses at the São Joaquim farm, in the city of Araçariguama (southeast São Paulo State). The 850 horses produce antibodies against the venom, which are then extracted from their blood to form the serum in a process that takes six to eight months. According to Dr. Wen, the Ministry of Health needs 80,000 ampoules of anti-scorpion serum per year, produced at Butantan, at the Instituto Vital Brazil in Rio de Janeiro, and at the Ezequiel Dias Foundation in Minas Gerais.
“Accident prevention is very important. This involves cleaning areas where scorpions live and preventing the accumulation of garbage,” recommends Bucaretchi, of Unicamp. Experts consider as minimally effective a strategy recently reported as being adopted in cities in São Paulo State: raising chickens in the backyards of houses or condominiums. The reason is simple: although chickens are natural predators of arthropods, they are active during the day and scorpions are nocturnal creatures.
In the past, even more unusual solutions have been implemented. At the beginning of the 1950s, residents of Ribeirão Preto, then with a population of approximately 80,000 people (now around 600,000), used two insecticides that have since been banned, benzene hexachloride (BHC) and dichlorodiphenyltrichloroethane (DDT), to stop an infestation of scorpions—about 10,000 were captured in bathrooms, bedrooms, kitchens and backyards between 1949 and 1951, according to a report in the American Journal of Tropical Medicine and Hygiene. There were radio and newspaper campaigns, lectures in school, collection points scattered throughout the city, and a prize, offered by the mayor, for the student who collected the largest number of scorpions.
1. Study of the toxins Ts6 and Ts15 of the scorpion Tityus serrulatus as potential therapeutic drugs for the treatment of autoimmune diseases (nº 2012/12954-6); Grant Mechanism Postdoctoral Research Grant; Principal Investigator Eliane Candiani Arantes – Ribeirão Preto School of Pharmaceutical Sciences (FCF-RP) of the University of São Paulo (USP); Recipient Manuela Berto Pucca; Investment R$235,699.44.
2. Toxic potential analysis of proteases and peptides present in the scorpion Tityus serrulatus venom and the blockage capacity of commercial antivenoms: enhancing the knowledge of venom and its mechanism of action (nº 2015/15364-3); Grant Mechanism Regular Research Grant; Principal Investigator Fernanda Calheta Vieira Portaro – Butantan Institute; Investment R$97,681.32.
MONTEIRO, W.M. et al. Scorpion envenoming caused by Tityus cf. Silvestris evolving with severe muscle spasms in the Brazilian Amazon. Toxicon. V. 119, pp. 266-269. 2016.
BUCARETCHI, F. et al. Clinical consequences of Tityus bahiensis and Tityus serrulatus scorpion stings in the region of Campinas, southeastern Brazil. Toxicon. V. 89, pp. 17-25. 2014.
PUCCA, M.B. et al. Immunosuppressive evidence of Tityus serrulatus toxins Ts6 and Ts15: Insights of a novel K + channel pattern in T cells. Immunology. V. 147, No. 2, pp. 240-50. 2016.
SILVA, T.L. da. The scorpion problem in Ribeirão Preto, São Paulo, Brazil. Notes on epidemiology and prophylaxis. American Journal of Tropical Medicine and Hygiene. V. 108, No. 3, pp. 508-513. 1952.