Immunisation back on the health map

By Nilma DOLE
 

Immunisation against vaccinable preventable diseases is a health achievement that Sri Lanka prides itself on with no cases of smallpox and the last reported case of polio in 1993 among other immunisation achievements. There is always interest in immunisation because of the benefits of injecting a little vaccination to stop some of the world’s deadliest diseases and Sri Lanka has been one of the best countries in the world for making full use of immunisation methods and implementing it in a national immunisation program.

Be it smallpox, polio or even rubella, immunisation has saved us from getting terribly sick and being less of a health burden for our country.

Consultant epidemiologist, Dr. Sudath Peiris of the Epidemiological Unit, Ministry of Health explained about the the history, introduction and new developments of the Mumps/Measles/Rubella (MMR) vaccine into the National Immunisation Program. The problem is that Sri Lankans have never seen the consequences of diseases so they don’t understand the gravity of the problem. Hence, the rubella controversy sparked a fear among the public that finally spurred some rubella cases. However, with changes in the national immunisation policy and the public restoring their faith in the immunisation system, Sri Lanka can be successful at eradicating diseases which are vaccine-preventable.

Speaking at the Health Education Bureau at an immunisation seminar, Dr. Peiris elaborated more about the importance of immunising against mumps, measles and rubella. He said, “The mumps virus belongs to the family Paramyxoviridae and only one serotype of mumps virus exists. Humans are the only known natural host for mumps virus and the virus is spread via direct contact or by airborne droplets from the upper respiratory tract.” He said that the incubation period averages 16 to 18 days with a range of two to four weeks where the sufferers can have myalgia, headache, malaise and low-grade fever followed by the characteristic unilateral or bilateral swelling of the parotid glands (located behind the cheeks). “Unless complications occur, the illness resolves completely because in approximately 30 percent of the cases, infection passes with non-specific symptoms only or without symptoms at all,” he said.

There is no specific therapy or cure for a mumps infection. “Natural infection confers lifelong protection against the virus but recurrent mumps attacks have been reported,” he said. It hasn’t been proved whether boosting the circulating wild virus in the community is a prerequisite for lifelong immunity but research is on-going. “Asymptomatic pleocytosis in the CSF (Cerebrospinal fluid pleocytosis) is found in 50 to 60 percent of mumps patients,” he said. According to him, symptomatic aseptic meningitis is reported in up to 15 percent of the cases. “Mumps encephalitis (without signs of meningitis) can occur in 0.02 to 0.3 percent of all mumps cases and deafness can occur in about 25 percent of such cases,” he said. He said that acquired sensorineural deafness instigated by mumps is one of the leading causes of deafness in childhood affecting approximately five in 100, 000 mumps patients. “Mumps orchitis occurs in 20 to 50 percent of post-pubertal males,” said Dr. Peiris.

He said that orchitis is not associated with permanently impaired fertility but a history of mumps orchitis may be a risk factor for testicular cancer. Moreover, the biggest threat of mumps is in pregnancy which would mean big problems in the long run. “If mumps is contracted during the first 12 weeks of pregnancy, there is a 25 percent incidence of spontaneous miscarriages,” said the doctor.

There is even a possibility of acquiring pancreatitis as a complication in approximately four percent of the cases reported. The disease burden of mumps burns a huge hole in the pocket of the Sri Lanka health budget. “The estimated mumps disease burden in Sri Lanka amounts to 20,000 to 200,000 annually in Sri Lanka. This gives rise to 280,000 cases which amount to 2.8 million days of disability,” said Dr. Peiris. The present WHO (World Health Organisation) recommendations on the MCV1 (Measles containing vaccine) depends on epidemiology and programmatic considerations. According to specifications, the first dose is administered at nine months where infants were prone to disease and two doses given when the infant is between the age of six and nine months. The present WHO recommendations state that in order to ensure optimum population immunity, all children should be given a second opportunity for measles immunisation. Dr. Peiris said, “This is plausible because it should help reduce the number of unvaccinated children and to reduce primary vaccination failures (vaccinated children who do not seroconvert).” This is generally administered at the age of four to six years but the second dose may be given as early as one month following the first dose, depending on local programmatic and epidemiological situation.

“The coverage of 95 percent for the first dose and 80 percent for the second dose is listed by a panel of experts as one of five indicators of progress towards regional elimination of measles.

The second opportunity plays important role in increasing proportion of population with lifelong protection against measles, as boosting through natural infection gradually disappears,” said Dr. Peiris.

The existing Mumps Vaccine WHO Recommendations states that the first dose of the mumps vaccine should be given at the age of 12 and 18 months. The proposed MMR Vaccine schedule will commence from October 1, 2011 for the first dose at the age of one and the second dose at three years.

“The proposed changes to the National immunisation schedule will commence from October 1, 2011. This won’t be any different to the traditional immunisation procedure but an update of the existing immunisation program,” said the epidemiologist.

The measles vaccine starts from nine months to one year as the first dose of MMRV, then the LJEV (Japanese encephalitis) vaccination is given as the first dose from one year to nine months and finally, the MR vaccine is given at three years as a second dose of the MMR. “The MMR vaccine could be offered to females in child bearing age (16 to 44 years) as a rubella containing vaccine instead of the traditional rubella vaccine,” said the doctor.

At present, the measles vaccine schedule offers the first vaccination opportunity at nine months as the measles vaccine.

The second opportunity is at three years as the measles/rubella vaccine. In the rubella, the first opportunity is administered at nine months as the measles vaccine and the second opportunity is at three years as the MR vaccine. With changes in the National Immunisation program, the public shouldn’t worry if it is successful. Countries in Europe and America have been following the updated immunisation policies for years with success.

“If we want to make our country successful, we should start by creating a healthy nation free of disease and those who are not a burden to our health sector financially.

In this way, immunisation is the way forward in creating a nation free of disease,” said Dr. Peiris.

Deadly link between high salt intake and obesity

Dietary salt intake and obesity are two important risk factors in the development of high blood pressure. Each packs its own punch, but when combined, they deliver more damage to the heart and kidneys than the sum of their individual contributions.

Discovering the molecular mechanisms behind this lethal synergy has presented a challenge to scientists, but research led by Toshiro Fujita, MD, suggests that high dietary salt intake and obesity work together to trigger an abnormal activation of a cellular protein called Rac1.

Obesity and a high-salt diet

Dr. Fujita’s team studied the effects of a high-salt diet in rats bred to have high blood pressure and different levels of blood pressure sensitivity to salt.

When obese “salt-sensitive” rats were fed a high-salt diet, the team found that Rac1 activated the mineralocorticoid receptor (MR) on the rats’ kidney cells. This receptor is normally activated by the hormone aldosterone. When turned on, MR leads to the expression of a protein called epithelial sodium channel (ENaC) and an enzyme called the sodium pump. Both of these substances promote the reabsorption of salt, which causes the body to retain fluid and results in high blood pressure.

wThis is the first time scientists have seen Rac1 usurp aldosterone’s role in activating MR in the regulation of blood pressure. The protein’s usual duties entail regulating an array of cellular events such as cell growth. The team made the discovery when attempting to treat the obese, hypertensive rats with drugs designed to block MR activation and inhibit Rac1. When Rac1 inhibitors were successful in lowering the rats’ blood pressure, the team knew they had discovered a mechanism by which obesity and a high-salt diet team up to wreak havoc on blood pressure and the kidneys.

Findings

According to Dr. Fujita, the team’s findings carry important implications for the treatment of hypertension. “Our data indicate that the Rac1-mediated pathway in the kidneys can be an alternative therapeutic target for salt-sensitive hypertension and salt-mediated kidney injury,” he said.

“Based upon our results, we can speculate that Rac1 in the kidneys regulates salt susceptibility of blood pressure, and that Rac1 inhibitors, as well as MR antagonists, may be effective in the treatment of salt-sensitive hypertension.”

- Japan Department of Internal Medicine

Genetic factors behind high blood pressure

High blood pressure is a well-known risk factor for heart disease. Researchers at the Sahlgrenska Academy at the University of Gothenburg, Sweden, have participated in an international study of 200,000 Europeans which has identified 16 new genetic variations that affect blood pressure. The discovery, presented in Nature, is an important step towards better diagnostics and treatment.

A billion people worldwide suffer from high blood pressure and are therefore in the danger zone for the likes of heart disease and stroke. Effective prediction and control of high blood pressure is therefore one of the most pressing global health issues.

Analyzing genetic data

Researchers from the Sahlgrenska Academy at the University of Gothenburg are among an international consortium of more than 400 researchers from the US, Europe, Asia and Australia hoping to identify which parts of our genes influence blood pressure by sifting through vast quantities of genetic data.

2.5 million DNA variations

In their latest study, the researchers analysed more than 2.5 million DNA variations from more than 200,000 Europeans.

The results, published in the renowned journal Nature, reveal 16 previously unknown genetic regions with interesting genes that regulate the body’s blood pressure both the lower level when the heart expands (diastolic) and the upper level when the heart contracts (systolic).

Genetic risk groups

With the help of these newly discovered genetic variations, the researchers have constructed genetic risk groups to help predict the risk of strokes and heart attacks.

“We’ve been able to classify individuals on the basis of how many risk variants for hypertension they have in their genes” says Fredrik Nyberg, a researcher from the Sahlgrenska Academy working on the project.

Important step forward

In another study published at the same time in Nature Genetics, the researchers from Gothenburg identify additional new genetic regions and genes controlling two other measures of blood pressure: pulse pressure (the difference between systolic and diastolic) and mean arterial pressure (an average of systolic and diastolic).

The study shows how important it is to analyse different measures of blood pressure. For example, pulse pressure is a marker of rigidity in the arteries carrying blood from the heart to the body, and different genes seem to control different aspects of blood pressure.

The results of the two studies are considered to be an important step towards understanding how the body regulates blood pressure, and the newly discovered genetic regions are potential targets for future treatments.

- M.N.T.

Yawning, not just a sign of sleepiness

Though considered a mark of boredom or fatigue, yawning might also be a trait of the hot-headed. Literally.

A study led by Andrew Gallup is the first involving humans to show that yawning frequency varies with the season and that people are less likely to yawn when the heat outdoors exceeds body temperature. Gallup and his co-author Omar Eldakar report in the journal Frontiers in Evolutionary Neuroscience that this seasonal disparity indicates that yawning could serve as a method for regulating brain temperature.

Gallup and Eldakar documented the yawning frequency of 160 people in the winter and summer with 80 people for each season.

They found that participants were more likely to yawn in the winter, as opposed to the summer when ambient temperatures were equal to or exceeding body temperature. The researchers concluded that warmer temperatures provide no relief for overheated brains, which, according to the thermoregulatory theory of yawning, stay cool via a heat exchange with the air drawn in during a yawn.

Gallup describes the findings

This provides additional support for the view that the mechanisms controlling the expression of yawning are involved in thermoregulatory physiology. Despite numerous theories posited in the past few decades, very little experimental research has been done to uncover the biological function of yawning, and there is still no consensus about its purpose among the dozen or so researchers studying the topic today.

“Enter the brain cooling, or thermoregulatory hypothesis, which proposes that yawning is triggered by increases in brain temperature, and that the physiological consequences of a yawn act to promote brain cooling.

“I participated in a study that confirmed this dynamic after we observed changes in the brain temperature of rats before and after the animals yawned.

“The cooling effect of yawning is thought to result from enhanced blood flow to the brain caused by stretching of the jaw, as well as countercurrent heat exchange with the ambient air that accompanies the deep inhalation.

“According to the brain cooling hypothesis, it is the temperature of the ambient air that gives a yawn its utility.

“Thus yawning should be counterproductive - and therefore suppressed - in ambient temperatures at or exceeding body temperature because taking a deep inhalation of air would not promote cooling. In other words, there should be a ‘thermal window’ or a relatively narrow range of ambient temperatures in which to expect highest rates of yawning.

“To test this theory in humans, I worked with Omar Eldakar to conduct a field-observational experiment that explored the relationship between ambient temperature and yawning frequency. We measured the incidence of yawning among people outdoors during the summer and winter months in Arizona. Summer conditions provided temperatures that matched or slightly exceeded body temperature (an average of 98.6 degrees Fahrenheit) with relatively low humidity, while winter conditions exhibited milder temperatures (71 degrees Fahrenheit on average) and slightly higher humidity. We randomly selected 160 pedestrians (80 for each season) and, because yawning is contagious, had them view images of people yawning.

“Our study accordingly showed a higher incidence of yawning across seasons when ambient temperatures were lower, even after statistically controlling for other features such as humidity, time spent outside and the amount of sleep the night before. Nearly half of the people in the winter session yawned, as opposed to less than a quarter of summer participants.

-US National Institute of Health