Physicians seeing increase in brown recluse spider bites

The brown recluse spider has a violin-shaped marking on its back. Credit: CDC image library

Vanderbilt medical toxicologists are reporting an increase in patients seen with brown recluse spider bites this summer.

The venomous bites usually heal well if left alone, according to Tennessee Poison Center Medical Director Donna Seger, M.D., but there are so many urban legends about these bites, patients frequently apply many treatments before seeking medical advice.

There are two components to spider bites -- the cutaneous lesion and, more rarely, the systemic symptoms that can occur following the bite. The syndrome known as systemic loxsoscelism consists of brown recluse spider bites accompanied by a fever, rash, muscle pain, with or without hemolysis (breaking down of red blood cells), which can be life threatening, especially in children, Seger said.

"Our recommendations are that all children under 12 with a brown recluse spider bite should have a urine test for the presence of hemoglobin in blood which indicates hemolysis," Seger said.

"If the urine is positive for blood and/or the child has other signs of systemic loxsoscelism (rash, fever), the child should be admitted and observed for hemolysis. If the urine dip is negative, and there are no other signs of systemic loxsoscelism, the child should be seen by a physician the next day."

If adults with a brown recluse spider bite do not have rash, fever or muscle pain there is no need to do a urine test, Seger said.

"As physicians, it is hard for us to do nothing. The cutaneous lesion has classic characteristics, but if physicians are not familiar with this bite, the tendency is to debride and cut out the lesion. This actually slows the healing process and can result in disfigurement that would not occur if the lesion were left alone. Ointments, antibiotics, and dapsone are not recommended. Ice works better than opiates for pain," Seger said.

"We don't know why systemic loxsoscelism occurs in some people with a brown recluse spider bite and not in others but it is life-threatening and does require immediate medical attention. Toxin-induced hemolysis can occur very rapidly and therein lies the life threat, especially in children."

The brown recluse spider, also known as the violin spider, is usually between 6-20 mm. It is typically light to medium brown but can range in color from cream-colored to dark brown or blackish gray. It has six eyes instead of eight and can be identified by the violin-shaped marking on its back.

Source: Vanderbilt University Medical Center

Mapping bats could help stop Ebola's spread

Fruit bats (Pteropodidae) are considered the likely host of the Ebola virus. Credit: Satit Srihin

In the fight against Ebola, mapping fruit bat habitats could be one important step, says a geoinformatics researcher at Sweden's Royal Institute of Technology.

Like the Black Death that ravaged medieval Europe, the Ebola virus' progress through remote areas of West Africa is enabled by lack of understanding about the disease, including its causes and transmission.

Mapping technology however will give responders to the crisis in Africa the upper hand in stopping the spread of the deadly disease, says Skog, a researcher in geoinformatics at Sweden's KTH Royal Institute of Technology.

Skog's research has produced a method that medical professionals can use to visualise the geographical distribution of a disease over time. In his research, Skog has explored the relationship between geography and disease distribution in major epidemics of the past, including the Black Death, the Russian Flu pandemic of 1889, the Asiatic Influenza of 1957 and the swine flu. He says the historical data provides a basis for predicting the course of future epidemics and pandemics.

"My research and method can also be used to report the current state of a pandemic, or predict how extensive the spread will be. And where the disease will strike next," Skog says.

In fact, the way in which Black Death spread during the mid 14th, century bears a no small resemblance to today's Ebola epidemic, he says. Both diseases were hosted by small mammals -- black rats and fruit bats, respectively. But ultimately it was humans that enabled its spread.

"The Black Death was very much depending on total lack of knowledge regarding the etiology of the disease and how to avoid further transmission," Skog says. "That is also the case for the mainly remote locations where Ebola now is spread."

Fruit bats are believed to be the natural hosts of Ebola. These bats are among the creatures that residents of rural West Africa hunt for "bush meat." The disease is also spread by the droppings of the bat, and it is believed to have spread to other types of bush meat, as well as monkeys and pigs that are raised for slaughter.

"The local population is getting part of their nourishment from bush hunting, leading to contact with the virus that is transmitted via body fluids," Skog says, suggesting that closer study of the fruit bat could provide vital answers.

"A guess of mine is that the number of infected fruit bats is a determining factor for an Ebola outbreak," he says. "Are there any known factors that may have changed the ecosystem in favor of the bats? Are the bats affected by the virus too? Do fruit bats always carry the Ebola virus or is the virus fatal to them as well? If so the percentage of infected bats will vary over the years also depending on the immunology of the species."

There are a number of geoinformation technology options available to public health organizations that have sent field crews to respond to the crisis. These, Skog says, including equipping field workers with hand-held GPS devices that feed a central database with data and findings regarding locations of bodies, possible infections and diagnosed cases personnel.

"The data can easily be centrally monitored and used for decisions and policies to mitigate the spread," he says. "Using satellite imagery, population centers can be localized. Collected disease data can also be compared and analysed with environmental and climatologic data to support other efforts to control the spread."

For instance, assuming that fruit bats are the reservoir for the ebola virus, Skog says it would be of interest to find out if the first detected cases in an outbreak are located in or close to a fruit bat habitat. "If the environmental and climatologic parameters for fruit bat habitats can be defined, there is a chance these habitats could be mapped using existing map data and satellite or airborne imagery," he says.

"Then risk areas could be monitored and preventive measures could be performed by health authorities. If the natural reservoir is in fact some other animal, positioning the first cases in each outbreak would still give a clue about what to look for."

Source: KTH The Royal Institute of Technology