Rat fever - a disease transmitted from animals to man

by Dr. M.C.L. de Alwis

* Rat fever has been recognised for over a century

* During the past decade it has been recognised as an emerging disease, globally

* Predominance of the disease among male paddy field workers could have an adverse impact on paddy cultivation

* Animals other than rats can play a vital role in transmission to man

* A collaborative effort of animal and human health workers will be necessary to curb its emergence

The incidence of rat fever in Sri Lanka has been increasing in alarming proportions, it hit the front page headlines of the Sunday Observer of 23rd November.

This news item quoting several medical specialists made some startling revelations that 6,400 cases have been reported during the past six months, and that of these 83% were males from the farming community compared with 4,500 cases reported in the past five years.

It is indeed a rapid increase. This situation is not surprising as it is reported that it has during the past decade emerged as a globally important infectious disease.

There are over 200 diseases recorded globally as communicable from animals to man. Of these, the WHO has listed 17 important diseases that receive their attention.

Leptospirosis (as rat fever is called scientifically) is one of them. Among the more familiar diseases in this list are rabies, anthrax, mad cow disease and animal influenza.

Leptospirosis was first reported clinically by Adolf Weil in 1886, and is therefore also referred to as Weil's Disease. It was in 1907 that the causative bacteria Leptospira was identified. In different parts of the world at various times the disease has been known by various names such as canicula fever, cane field fever, manukayami fever and seven days fever.

The causative organism is a spiral - shaped bacterium belonging to the family of bacteria known as spirochaetes. There are over 200 types of leptospirae recorded but only five of these are commonly associated with human disease. It needs moisture for its survival and hence the disease prevalence is higher in wet swampy regions or during rainy seasons.

Originally, the disease was found to be transmitted to man through contamination of food and water with rat urine, as the organism is shed in the urine of infected animals' hence the name rat-fever. Subsequently, Leptospirosis has been reported from a wide range of animals - dogs, cattle, sheep, pigs, deer, rabbits, hedgehogs, raccoons and skunks, in different parts of the world. Domestic dogs can become infected by drinking water from wayside pools or drains contaminated with urine of infected dogs, or by licking the urine or genitals of infected dogs. Dogs, however, can be protected by the use of a vaccine - DHL triple vaccine covering distemper, hepatitis and leptospirosis.

Human infection from animals

Human infection occurs through contact with food, water or soil contaminated with urine of infected animals. Drinking water from or bathing in stagnant pools are common avenues of infection.

In Sri Lanka, apart from infection in dogs, little information was available till recently on the status of other animals species. In the early 1990's a research study was made at the Veterinary Research Institute of the Leptospirosis status of buffaloes working in paddy fields. The increasing incidence of the disease among paddy farmers reported by the Health Department prompted this study.

This study was confined to buffaloes, as it was part of a research programme on the indigenous water buffalo, funded by the Swedish Government. Scientists at the Veterinary Research Institute conducted this study on around 1,500 buffaloes that were selected from the paddy fields in areas where the Department of Health Services reported the highest incidence of leptospirosis among farmers. It was revealed that in different districts, approx 10%-40% of buffaloes had antibodies against the types of leptospira causing human disease. This did not necessarily mean that so many buffaloes were clinically suffering at that time, but indicated that they had been infected at some point in their lifetime.

Urine samples from some seropositive buffaloes were cultured at the VRI and leptospira of the types that caused human infection were identified. These cultures were then sent to the World Reference Centre for Leptospirosis, in Victoria, Australia and the identification was confirmed.

Human infection can occur through skin abrasions, or intact mucous membranes - mouth, eyes, respiratory tract.

In the paddy field during ploughing, the farmer walks immediately behind the animal used for ploughing and therefore directly exposes his feet to fresh urine shed by the animal. Any minor skin injury in his feet could be the route of infection.

Further, particularly from female animals when urinating, depending on the wind direction the farmer would inhale a spray of urine, and this could very well be an important mode of infection.

In this situation, the fact that 83% of those infected in the farming community are males is not surprising.

Whilst one cannot disregard the role of field rats, their contribution is insignificant in comparison with buffaloes and cattle, when the volume of urine shed and the contact with man is concerned.

The findings of the study in buffaloes should be correctly interpreted. It would be wrong to conclude that such a high percentage of buffaloes in Sri Lanka are infected.

The sample tested was not a cross section of the buffalo population in Sri Lanka. It was a biased sample from selected, highly infected area and secondly, what is true for buffaloes could be true for cattle used in the paddy field as well.

Prevention

The disease is not reported to spread from person to person. Unlike in animals, where recovered animals may continue to shed infective bacteria, dissemination of bacteria by convalescing humans is reported to be extremely rare. Thus, any preventive measures should seek to eliminate the disease in animals and also prevent the animal - to - man transmission. The likely modes of infection to man outlined above will provide the clues as to possible methods of achieving the latter objective.

What appears to be necessary is a collaborative effort by the animal and human health personnel. To control this disease, which apart from being a burden of the Health Services, will also have an economic impact. Loss of man days among paddy farmers would be of considerable significance, during cultivation seasons.

It is also important to educate and carry out awareness programmes among farmers in endemic areas. It is hoped that the relevant ministries will consider this problem with the seriousness it deserves.

(The writer is a former bacteriologist and Head of the Veterinary Research Institute.)

Monitoring mental health by text

Every morning at precisely 10 am Joe (not his real name) gets a text message from his clinician, asking how he is feeling.

From the data received the medical team can plot his mood swings, monitor how his medication is working and assess when he needs his next face-to-face appointment.

Joe, aged 23 and from Sussex, said that for him the system has been brilliant and has cut down the amount of time he needs to spent with the doctors for his bipolar disorder.

"For me it has fortunately proved to be extremely effective. Whereas before I would be going to see the doctors once a month or more now I only need to see them every three months to check that all is well," said Joe.

Mood monitoring

"From my perspective the phone texting has been a godsend."

Each patient using the scheme is given two small cards, marked with mood variations from A to E, which allow them to plot their moods for the previous week - depression and euphoria. They then select which feeling most closely matches theirs and text over the corresponding letter.

Joe said the system provided an excellent support network.

"It is a simple thing, but because it is so regular it gives you a structure and giving the strong impression that someone at the other end is taking your data," said Joe.

"If there is a blip or hiccup they can check against medication you can tell what effect taking a pill or adding a pill can cause.

"And if they see an anomaly in your results they will contact you.

"It has been a massive support for me," he said.

Pain free recovery

Joe's treatment has been so successful he has been able to return to university to complete his degree.

"That is thanks to the service, because without it the treatment could have taken twice as long. It has made recovery relatively painless," he added.

The system, a collaboration with Oxfordshire and Buckinghamshire Mental Health and Oxford University's Department of Psychiatry, has been such a success that it is now being expanded across the trust later in the new year.

Professor John Geddes at Oxford University said that over 150 patients now self-monitor and that they also collect data from patients elsewhere in the UK and in Colorado, the US, for use by their own clinicians.

Professor Geddes said the mood monitoring was vital.

"When you try to work out how their mood has been there are real problems trying to do that retrospectively," said Professor Geddes.

"What people tend to do is either miss really important mood variability or just look at the average or very severe.

"Before I would spend quite a lot of time trying to find out how the patient had been and if the patient was depressed it could be quite hard for them to remember.

"Basically, with this system we would hit the ground running and we can focus on trying to help them and their treatment."

Professor Geddes said the system could probably be adapted to monitor people with other mental health disorders, such as less severe schizophrenia.

"Monitoring your mood on a daily basis is a foundation of self management of the illness," he said.

"To have a mood mapping text messaging service to a health professional will provide a window into your illness. This could lead to early intervention and potentiality head off serious episodes of this mood disorder."

BBC News

`Bug' could combat dengue fever

Humans could be protected from dengue fever by infecting the mosquitoes carrying it with a parasite which halves their lifespan, say researchers.

Australian scientists, writing in the journal Science, found that Wolbachia bacteria spread well through laboratory-bred mosquitoes.Only older mosquitoes pass on dengue - so killing them could cut disease. Experts said it remained to be seen how well the bacteria would spread outside the laboratory.

The virus might also adapt to survive, they added. Many thousands of cases of dengue fever occur worldwide each year, mainly in warmer tropical countries.

The virus is passed to humans when mosquitoes carrying it feed on their blood, and while there have been efforts to eradicate them using insecticides, these have been fraught with problems, including the ability of the mosquito to become resistant to the chemicals used.

The potential of Wolbachia as a way of controlling mosquito populations has been suggested for some time, but the latest study offers hope - albeit under laboratory conditions - that it might work.

The researchers from the University of Queensland in Brisbane picked a strain of Wolbachia known to halve the lifespan of its host. The mosquito which carries the dengue virus is not naturally susceptible to the bacteria, so the researchers adapted it to create a successful infection.The bacteria can be passed from infected female to offspring, and even though the cost in terms of lifespan should mean that infected insects should die out, Wolbachia has another trick up its sleeve.

It makes subtle changes to infected males which mean they can only produce offspring with infected females.

As expected, the infection thrived in the laboratory population of mosquitoes, and halved their lifespan to just a few weeks.This is potentially significant because, after a mosquito acquires the dengue virus by biting an infected animal or human, there is a period of incubation lasting from a week to three weeks before it can pass on the infection when biting.This means that only mosquitoes older than this are likely to be dangerous to humans and even these are likely to die swiftly, reducing their ability to infect.

The researchers suggested that the parasite represented a potentially inexpensive way to tackle the problem, particularly in urban areas, where other methods of control were difficult.

Dr. Andrew Read and Dr Matthew Thomas, specialists in infectious disease dynamics from the Pennsylvania State University in the US, said "substantial" reductions in disease transmission could occur, but there were still obstacles to success. "Determining whether it can remove enough infectious mosquitoes will be a challenge," they wrote.If the bacterial strain chosen was too virulent it would spread very slowly and large numbers of infected mosquitoes might need to be released, they said. It was also possible that dengue virus strains would adapt to require a shorter incubation period, they said.

BBC News

`Vedasa' Medical Exhibition 2009 at BMICH

The Faculty of Medical Sciences of the University of Sri Jayewardenepura has organised a medical exhibition from January 6 to 12 to commemorate the golden jubilee of the University which falls this year.

A relatively young medical faculty with a short but proud history of 15 years, it has made its mark in the field of medical education having had the distinct honour of its students being placed first in the order of merit for the last 5-6 years. The graduates have excelled in their postgraduate exams here and abroad and are working as eminent consultants in their respective fields.

The exhibition is to be totally student-centered and is based on the module system of the new curriculum commenced in 2006. This includes stalls depicting the normal and abnormal of the central nervous system, cardiovascular, respiratory, gastrointestinal, renal, reproductive and special senses. In addition there would be stalls relating to mental health, malignancies and orthopaedics and trauma.Common diseases like diabetes would be given a special place with communicable diseases such as filariasis, malaria, tuberculosis, leprosy and much talked about dengue, chickungunya and other emerging diseases being presented with the help of the respective control programs and the epidemiology unit of Sri Lanka.

Sexually transmitted diseases and AIDS along with anti alcohol and drug abuse will be interestingly presented with powerful messages and dramas, amply supported by the STD/AIDS campaign and Anti Drug Information Centre (ADIC).The much looked forward display of dissected bodies and those being dissected will be a separate stall. A stall relating to forensic pathology with display of firearms, bombs and genetics in forensics will be a popular attraction. An interesting display of varieties of snakes of Sri Lanka will be presented by the Nature Club of the Faculty with the collaboration of the Zoo. There will be demonstrations and "street plays" relating to home emergencies and first AID.

Another different aspect of the exhibition would be the "Theme days" discussing topics of public interest such as "Childhood obesity, Adolescence and health, Physical exercise and health, Occupational health, Home accidents, Pests and disease which would include the fast spreading Leptospirosis. These will be presented during the six days of the exhibition at scheduled times and would take the form of panel discussions, lectures, film shows etc.