Tracking the spread of sickness and disease

Spraying Mosquitoes Could Prevent West Nile Virus

By: Jennifer Madison. July 14, 2013

When it comes to the administration of preventative measures for infectious disease, there has always been some contention. When one party claims a particular method is perfectly safe, another will claim it’s harmful. And while none of us want to see the geographical spread of disease grow, it’s vital that hard facts can back up the efficacy of preventative measures. Thanks to a recent study from the University of California in Davis, which analyzed the results of aerial mosquito spraying, those hard facts may be at our fingertips. The study, which appears in the June 2013 issue of the Public Health Report, claims that spraying mosquitoes from the air actually has no negative side effects for humans in the area. This is contrary to a popular belief that such measures could be harmful, as with pesticides and other aerial sprays.

What this means for West Nile Virus

West Nile Virus, or WNV, is a well-known disease in the United States and is transmitted to humans from mosquitoes. At the present time there are no medications to treat the disease and no vaccine; however, many sufferers do not have any symptoms at all and can simply ‘carry’ the disease with no ill effects. However, around 1 in 5 people will develop a fever, bodily aches, rashes, vomiting and other symptoms. And beyond that, 1% of sufferers will develop long-term untreatable neurological problems. For this reason, it is necessary to find ways to prevent the spread of West Nile Virus. With a lack of treatment options, the only prevention is to reduce the population of mosquitoes that carry the disease – and aerial spraying could well be the answer.

The UC Davis study on mosquito spraying

The team at UC Davis took an interest in the effects of spraying pesticides and insecticides from planes on the local human population. In order to build a picture of these health implications, the team looked at a period of time in 2005 immediately following the aerial spraying of chemicals in the California area. They then looked at the medical records and reports which detailed the visits to emergency rooms in that same area. Their results were encouraging: there was no evidence that the spraying of pesticides increased the reports of diagnoses usually associated with exposure to such agents. This included respiratory, gastrointestinal and neurological symptoms. The team analyzed more than 250,000 ER visits and whilst there were some incidences of these symptoms, they were not statistically significant enough to prove a cause and effect relating to aerial spraying.

Is there a risk to public health?

The results of the UC Davis study are enough to suggest that aerial spraying should be considered in the control of mosquitoes to prevent WNV. Spraying is already known as a potential means of population control for mosquitoes, so it seems that it should now be a viable candidate to aid in the reduction of these populations. It’s especially surprising to see public concern about air contamination and harmful effects of pesticide spraying when there are more prevalent issues which cause higher risks. Smoking in public, for example, has been proven to cause a wide range of damaging effects, even though it is only passive inhalation. And despite the fact that each year more and more people are seeking help to quit smoking, there is still a very real risk to the quality of the air in public places. With such an argument, it’s difficult to see any valid reason not to at least attempt to use aerial spraying as a means of preventing the spread of West Nile Virus, at least in the short-term.

What about the long-term?

Here lies the rub: the study carried out by the UC Davis team only looked at a small sample window following aerial spraying in 2005. The health effects on these individuals in the years that followed were not included in this study. This missing data may prove to be critical. On the one hand, spraying for mosquitoes could actively reduce the insect population and reduce incidents of WNV, but on the other, we could see some ill effects presenting themselves in years or decades which will never be linked to this spraying. It’s a difficult decision, and it’s arguments such as these that maintain the contentious nature of the aerial spraying debate. Only time will tell if local authorities decide to take the risk to potentially better protect their residents.