Transcriptome Sequencing Used to Screen For Human-Animal Disease

Recent development in genetic sequencing are being used to spot diseases in wildlife that other diagnostics cannot detect.

In a recent issue of Biology Letters, a study led by Duke University has used whole-transcriptome sequencing to screen for blood-borne diseases that are found in wild lemurs. These animals are known to be distant primate cousins to us human beings.

Lemurs were found to carry a number of strains of parasites that are similar to those that cause diseases in humans such as Lyme disease.

This is the first time that these parasites have been detected in lemurs or also in Madagascar, which is the only place where lemurs live in the wild.

Transcriptome Sequencing

This technique could actually make way for earlier and more accurate ways of detection future outbreaks of diseases transmitted between animals and humans.

Anne Yoder, co-author of the study and director of the Duke Lemur Center, says that the technique enables us to detect pathogens that are unexpected and become better prepared for them.

Last 2012, Duke Lemur Center veterinarian Cathy Williams and her team started performing physical exams on lemurs living in the rainforests located near a mining site in Madagascar in order to determine what the effects of such activities are on the health of lemurs.

Lemur populations are becoming increasingly small and fragmented because of human activities like mining, logging and clearing forests to make way for cattle grazing and rice paddies. If an infectious disease wipes out a lemur population it could be a huge blow to the species, says Williams.

Aside from doing physical exams, the team of researchers also took blood from the lemurs and tested them for exposure to currently known viruses and pathogens, but they were not able to find anything.

Williams also adds that the limitation of standard tests is that they only aim to detect known pathogens. This is usually done by checking antibodies of certain viruses, or check parts of genetic material in the animal's blood. But in cases like this, you really need to know what you're looking for.

Because of this limitation, new or exotic diseases often slip in the hands of scientists and health experts. In order to deal with this, they tried a new approach.

Peter Larsen, lead author and senior scientist at Duke, analyzed blood samples of six lemurs from two species (indri and diademed sifaka). Both species are currently considered to be critically endangered by the International Union of Conservation of Nature (IUCN).

With current technology such high-throughput screening, which is the ability to read genetic code rapidly, Larsen and team were able to find that there was more than just lemur RNA in the blood. Using computer algorithms and genetic sequences from databases, they discovered some parasites that were reported for the first time in lemurs.

These included a new form of protozoa that causes babesiosis (disease from the bites of ticks) and a new kind of Borrelia that is similar to the bacterium that causes Lyme disease. Another is a bacterium called Candidatus neoehrlichia, which can be fatal to humans.

Performing researches such as this are very important as recent outbreaks, such as that of SARS, Ebola and avian flu, are zoonotic, which means that they are spread between wild and domestic animals, and humans.