Rebecca Traub recognised for outstanding contributions to parasitology

Professor Rebecca Traub is applying innovative solutions to improve public health of both humans and animals in developing nations, and conducting research that has earned her the Bancroft-Mackerras Medal for Excellence in parasitology.

The hookworm Ancylostoma ceylanicum was discovered by Clayton Lane in 1913 in the Indian city then called Calcutta. It was spotted in dogs and occasionally humans in many parts of Asia until the 1970s, but with infections regarded as ‘rare’ and ‘abnormal’ among humans, it was left to the annals of medicine.

“It was completely dismissed in humans as a rare and inconsequential zoonosis, a disease agent transmitted between animals and humans,” says Professor in Veterinary Parasitology Rebecca Traub from the Melbourne Veterinary School.

But almost a century later, Professor Traub says, she began looking into the scientific literature on this centimetre-long monster from her home city.

“In much of Asia, large populations of semi-domesticated community dogs share a close relationship with humans,” she says.

“In these communities, poor standards of sanitation and hygiene provide ideal conditions for transmitting zoonoses from animals to humans.”

“So, my curiosity got the better of me. Since all hookworm eggs look identical under the microscope, it was possible that A. ceylanicum in humans were being completely overlooked.”

Professor Rebecca Traub and her dog, Ruby. Photo: Stuart McEvoy, Newspix.
Professor Rebecca Traub and her dog, Ruby. Photo: Stuart McEvoy, Newspix.

Professor Traub developed an advanced molecular biology test that would distinguish the parasite’s eggs from similar species in stool samples. To her “utter amazement,” A. ceylanicum was present in not only many semi-domestic cats and dogs in the Asia-Pacific, but was the second most common hookworm species affecting humans in the region, comprising from 13-25 per cent of infections.

Cross-species diseases need a cross-species approach

Like most other hookworm species, A. ceylanicum waits in the soil for a host (in this case a human or dog) to step in the wrong place, then enters their body through the skin.

It makes its way to the small intestine where it sucks blood from their capillaries, causing abdominal pain, diarrhea and in some cases anaemia. Here it lays its eggs, which return to the environment via faeces, hatch and wait for their next victim.

Ancylostoma ceylanicum_braziliense head
The anterior of an Ancylostoma ceylanicum hookworm, showing the teeth it uses to latch on to a host’s intestine wall. Image: The University of Melbourne Parasite Library.

A. ceylanicum infections have been shown to cause abdominal pain and bloody diarrhea in humans. While long term effects of A. ceylanicum infections on human populations are unknown, long term infections of other species of hookworms can lead to impaired physical, mental and intellectual development among children, and increased mortality of pregnant women and their babies.

With a growing awareness of the burden hookworms and other infections regarded as ‘neglected tropical diseases’ pose on developing nations, the World Health Organisation has committed to eliminating disease caused by soil transmitted parasites by 2020 by regularly deworming at-risk groups like women and children. In 2017, over 598 million children were treated.

But the zoonotic nature of A. ceylanicum infections – that they also target and thrive in canine populations – creates an extra layer of difficulty for health organisations seeking to control the parasite.

“Unlike human hookworms, A. ceylanicum is a zoonosis, which means that unless dogs, the reservoir of infection, are targeted as part of these control programs, hookworm larvae will continue to contaminate the environment and provide a source of re-infection for humans,” Professor Traub says.

Professor Traub and her new colleague, Mackenzie Fellow Dr Vito Colella, have therefore been working with other health professionals, researchers and authorities to monitor and address A. ceylanicum by treating both human and dog populations in Asia, an approach to known as One Health.

Professor Rebecca Traub, Dr Vito Colella and local colleagues in Cambodia
Professor Rebecca Traub, Dr Vito Colella and local colleagues in Cambodia, where they are working with the Cambodian Ministry of Health to reduce or eliminate A. ceylanicum infections using a One Health approach.

One Health recognises that single-species or geographically limited control of diseases which affect and spread between different species in the environment will be limited in their effectiveness.

It seeks to address challenges that affect human, animal and environmental health by drawing on the expertise and collaboration of a range of clinicians and professionals including veterinarians, physicians, nurses, scientists, ecologists, and policymakers.

The need for specific local advice led her to found the Tropical Council for Companion Animal Parasites (TroCCAP) in 2016 to deliver guidance and best-practice recommendations for the treatment and control of parasites of companion animals such as dogs and cats in tropical and sub-tropical regions.

Spotting spotted fever’s host

Even in developed countries, zoonoses pose challenges to health authorities.

Flea-borne spotted fever (FBSF), a zoonosis caused by the transmission of Rickettsia felis bacteria to humans via the bite of a flea, is a rising public health concern in Australia. It’s been a research focus for Professor Traub and her research group over the past ten years.

After an outbreak struck a Melbourne family of five who had taken in infected kittens from a Lara farm in 2009, Professor Traub and her lab members Dr Sze Fui Hii and Dr Thomas Teoh worked with researchers from the Australian Rickettsial Reference Laboratory and Bayer Animal Health to re-test 49 samples that had tested positive for the murine typhus-causing R. typhi bacterium.

They found only seven of the samples were clearly R. typhi; 14 were R. felis, and the other 28 were indeterminate, and could have been either agent. It was very likely Australian patients clinically ill with FBSF were misdiagnosed, making the need for re-examination and increased awareness in the human and animal medicine community clear.

Rebecca Traub examines a community dog during a visit to Cambodia. Photo: Dr Vito Colella.
Rebecca Traub examines a community dog during a visit to Cambodia. Photo: Dr Vito Colella.

“In most cases flea-borne spotted fever goes unnoticed as flu-like illness, but on occasion can result in the absence of treatment, severe health consequences in humans, thus indicating the necessity of flea control in pet dogs and cats,” Professor Traub said.

Professor Traub and colleagues also have been investigating the role of dogs in the transmission of the disease to humans, with an upcoming publication indicating that – despite the name pointing the finger at their rival species – dogs are actually the natural reservoir for R. felis.

These discoveries, along with Professor Traub’s application of accurate and cost-effective tools to determine the prevalence and diversity of parasites affecting animals and humans in developing communities in Asia and the Pacific, have earned her the Bancroft-Mackerras Medal for Excellence from the Australian Society for Parasitology.

Professor Anna Meredith, Head of the Melbourne Veterinary School, congratulated Professor Traub for the recognition of her expertise.

“Rebecca is the latest Melbourne Veterinary School professor to receive this prestigious award, joining Ian Beveridge, Marshall Lightowlers and Robin Gasser,” she said.

“It is wonderful to see the School so strongly represented in the field of parasitology. This is a fitting tribute to our continuing excellence and high profile in this important aspect of animal and human health.”

Professor Traub received the medal at the Australian Society for Parasitology Annual Conference in Adelaide on Tuesday 9 July and delivered the Bancroft-Mackerras Medal Oration, titled “One Heath research: challenging the dogmas.”

“One advantage we have as veterinarians is that as animal health professionals, we are more aware of a whole-ecology approach to the diagnosis and control of zoonotic disease,” Professor Traub said.

“A One Health approach is about breaking the cycle of disease transmission at the animal and environmental level, and minimising the risk to humans by making sure all parts of the ecosystem are healthy.”

The oration will be published in the Meeting issue of the International Journal for Parasitology.

Story by Stuart Winthrope. Banner image: Professor Rebecca Traub with Professor Una Ryan, President of the Australian Society for Parasitology.