No doubt, after a scorching summer, the monsoon is a welcome sight, but with it comes hordes of pests and the ensuing diseases. The best way then to combat the monsoon maladies, says Nikhil Chatterjee, is to be one step ahead of your enemy – pests.
The rains bring in a host of problems every year, including water-borne and pest-borne diseases. Here it is important to make a distinction between the two terms because most people confuse the two and use either loosely when talking about monsoon illnesses.
Water or food-borne diseases – such as cholera, typhoid, gastroenteritis and infective Hepatitis (Hepatitis-A, of which jaundice is the chief symptom) – are caused by human consumption of contaminated food or water. On the other hand, pest or vector-borne diseases – such as malaria, dengue, and leptospirosis – are directly transmitted by pests, insects and rodents. An important aspect of vector-borne diseases is that the disease-causing organism, such as a protozoan, virus or bacteria, is carried by the vector in his body, where the organism completes a part of its lifecycle. In addition to being vectors, pests also spread food and water-borne diseases by contaminating food and water, adding another dimension to the term.
This article will focus on pests which cause pest-borne diseases, with a particular significance for public health during the monsoons.
Why the monsoons?
The summer months are usually marked by hot and dry conditions, which are not ideal for the survival of most disease-causing organisms. In addition, conditions are not favourable for host insects, which also need water (e.g. mosquitoes) and damp decomposing organic matter (e.g. flies), for propagation.
The rains bring down the temperature and create wet & humid conditions, creating an ideal ground for pests and diseases. Given the general unhygienic surroundings we live in, it is then no surprise that we find ourselves staring down the barrel of one epidemic or the other.
Flies
Flies thrive in moist places where there are garbage and faeces. They are active in daylight or in artificial light and rest at night on walls, fences, wires or other objects. The high humidity and abundance of moist, decomposing organic matter and garbage provide flies with perfect breeding grounds, in which fly larvae complete their development, explaining their large number seen buzzing around during the rains.
Common and filth flies are attracted by the smell of fermenting, rotting material or faeces and feed primarily on liquids or moisture from these. Dry food is dissolved by a secretion from the salivary glands and by regurgitating. They also seek food on moist skin surfaces such as the mouth, eyes, sores and wounds. Flesh flies breed by laying their eggs on decomposing flesh, which the larvae eat.
Flies spread various infectious diseases such as cholera, shigellosis, typhoid, salmonellosis, diarrhoea and dysentery by contaminating food. They also transmit parasitic worms which cause skin infections.
Flies can contaminate food just by sitting on it and they will sit as easily on both filth and human food; disease causing organisms and germs stuck to parts of their body (mouth, legs, body hairs) thus find their way into our stomachs. Flies also have a particularly disgusting habit when they land on our food; they regurgitate or vomit onto to it. This vomitus contains strong enzymes which break down the food into an easily digestible soup which the flies then suck up. Speaking of table manners, flies have another ace; they defecate while eating, yet another way of spreading contamination.
Fly Prevention Tips
- Ensure garbage is collected and disposed off in time
- Collect garbage in containers and these should have tight fitting lids
- Clean out and dry garbage containers regularly
- Doors closers should work properly and gaps around doors and windows should be sealed
- Broken glass and damaged insect screens in doors and windows should be replaced
- Identify and screen all vents & openings which could serve as fly entry points
- Fly breeding in surrounding areas should be prevented by eliminating garbage and organic debris
- Night illumination should shine onto buildings rather than from buildings
- Switch from mercury vapour to sodium vapour lamps
- Install adequate number of insect light traps and ensure they are five feet or below from ground level
- Check if air curtains, where installed, are fully functional
- Check if puddles form around the building after rain; these are to be eliminated
- Ensure drains are cleaned regularly and free from solid wastes
- Engage a professional pest management company for fly management in and around your (commercial) building.
