bacteria

Animal proximity causes hydrocephalus

PENN STATE (US) — Infant hydrocephalus in developing countries is most likely linked to farm animals and is caused in part by previous bacterial infection, according to an international study that finds the best approach is prevention.

“Hydrocephalus in infants in developing countries is a grand medical mystery,” says Steven Schiff, professor of engineering at Penn State.

Hydrocephalus is a build up of the fluid that normally surrounds the brain. The increased pressure causes the head to swell and damages brain tissue.

Treatment includes placing a shunt to drain the fluid, which inevitably becomes plugged, requiring emergency care, not always available in rural Africa and other resource-limited regions of the developing world.

New brain endoscopes can divert fluid buildup internally in such children, but doesn’t address the fluid and does not fix previous infection damage to the brain.

“Brains of children with hydrocephalus can be completely or mostly destroyed either by the scarring from the disease or by the pressure of the cerebrospinal fluid that cannot escape,” says Schiff.

“Many of these children with the worst aftereffects of infection will be mentally deficient and survive only as long as their mothers can adequately care for them. Understanding the causes could eliminate or prevent the enormous costs to lives and families that hydrocephalus brings.”

Hydrocephalus in infants in sub-Saharan Africa is thought to be caused most often by meningitis-type infections during the first month of life.

Researchers from the U.S. and Uganda looked at the fluid from the brains of three sets of 25 consecutive infant hydrocephalus patients during January, July, and October to try to determine the cause of the disease.

By the time parents bring infants with rapidly growing heads to the CURE Children’s Hospital in Mbale, Uganda, the underlying infection is gone. The researchers were unable to culture any bacteria from the samples.

To identify traces of previous bacterial infection, researchers used DNA sequencing to look for 16S ribosomal DNA that exists in all bacteria.

The findings, reported in the Journal of Neurosurgery: Pediatrics, show that 94 percent of the samples contained bacterial remnants. The researchers found a seasonal difference between samples representing infection during the dry season that were predominantly Betaproteobacteria and Gammaproteobacteria, that resulted from rainy season infection. Acinetobacter appeared in the majority of patients following rainy season infection.

Some sequences that appeared in the DNA analysis were from unknown bacteria and in many cases the bacterial fragments were not identifiable as to the type of Acinetobacter they represented.

In the United States and other industrialized countries, infant hydrocephalus is usually due to either a congenital anomaly or, in low birthweight premature infants, due to brain hemorrhages from immature blood vessels.

At one time, Group B Streptococcus was a common cause of postinfectious hydrocephalus in infants in industrialized countries, but now physicians test mothers for the infection and treat with antibiotics before they give birth and the infections are rare.

Surprisingly, Schiff says, none of the remnant DNA in the Ugandan infants was from Group B Streptococcus.

Looking for the source of the neonatal infections, the researchers targeted the living environment from infants with evidence of prior acinetobacter infection and located patients’ homes.

What they found were villages of huts where cow dung was pounded into the hut floors to keep water and ants out and used in patios around the huts where vegetation is cleared to protect against snakes. Newborns enter an environment where they not only live near animals, but also are surrounded by their material.

A sampling of both the cow dung floors and excrement from cattle, goats, and chickens found similar genetic sequences from the bacteria retrieved from the infants as in the hut floors and nearby dung.

“It is really hard to keep infants to an adequate standard of cleanliness in this environment,” says Schiff. “The bacteria we found reflects, I think, a significant environmental influence.”

While the researchers have not yet proven that these bacterial infections are the cause of the devastating hydrocephalus occurrences, they believe that in part, bacterial infections from animals are the cause.

Historically, certain East African peoples have applied cow dung to stem bleeding in umbilical cord stumps, which caused newborn infections. Although such infections are now rare, the scope of newborn bacterial infections related to living in close proximity to domestic animals remains poorly categorized.

“As far as we can tell, these types of environmental newborn infections are the dominant cause of hydrocephalus on the planet,” says Schiff. “We may be dealing with bacteria that we can’t culture, viruses or parasites, and we may be dealing with different organisms in different locations.”

Researchers from Harvard University contributed to the study.

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