Author : Ramanath Jha

Expert Speak Urban Futures
Published on Nov 06, 2024 Updated 0 Hours ago

New York City’s experiment with rodent contraceptives is an important new step towards rodent control

Fighting the rat menace in cities: The NYC experiment

Recently, New York City’s (NYC) proposed experiment with rodent contraceptives to combat rats became global news. The step was labelled by the city mayor as a “new paradigm in urban rat management.” The city council recently approved the deployment of ContraPest, a type of rodent birth control tool, to be tested in limited areas of the city.  Its developer, US biotechnology company SenesTech,  claims that it provides a humane and sustainable choice for long-term rodent management. Based on the success of the city’s trial,  a new approach might be taken to deal with NYC’s about 3 million rats. If successful, this experiment could mark a departure from traditional methods of rodent control.

Rats have been known to co-exist with humans in cities for centuries. They have also been a nuisance in cities all over the world.  They are a risk to human health and a danger to built structures, electrical cables, and parked cars. They could result in a major loss of food grains stored inside granaries. The World Health Organization (WHO) for instance, estimated that rat control measures in Mumbai alone could save enough food to feed 90,000 people annually. Studies conducted in India indicate that 2.5 percent of all food grains stored in India are lost to rodents. A conservative analysis estimated that between 1930 and 2022, rats caused a loss of US$ 3.6 billion to the world’s economy. Rats contaminate food and animal feed, introducing unwelcome parasites such as fleas, lice and ticks into the human habitat. They can cause allergies, rat bite fever, scrub typhus, leishmania and plague. At times, their activities could lead to salmonellosis (food poisoning).

The World Health Organization (WHO) for instance, estimated that rat control measures in Mumbai alone could save enough food to feed 90,000 people annually.

The COVID-19 pandemic, forced rats to discover new food sources. Rodentologists estimate that hundreds of thousands of rats were killed during the pandemic. But as businesses and eateries have become operational and returned, the resilient rats have rebounded, and their population has grown in cities across the globe. Furthermore, climate change, which brought  longer periods of warm weather, has given them more time for breeding.

Dealing with rats has not been easy. They are tenacious, highly adaptable, and prolific breeders. NYC has tried various methods in the past to tackle the menace. In 2023, the city council passed a new law that required contractors of construction projects to shoulder rat extermination costs. The law emphasised prevention over reaction and laid down strategies for rat control, which included  conducting regular inspections, identifying potential rat entry points (gaps in walls or floors) and sealing them, discovering signs of infestation early and eliminating them, adequately storing garbage and ensuring its safe disposal. Additionally, NYC has altered the trash take-out times for businesses and residents to prevent garbage from staying out too long on the streets, allowing rats to fester. The city now requires food-related businesses to dispose of their waste in secure containers instead of trash bags. To incentivise households, NYC also decided to replace the residents’ trash bins with larger cans at the cost of US$ 3.4 million.

Rats in Indian cities

Indian cities have had large rat populations for a long time and controlling rats has been an age-old responsibility of Indian Urban Local Bodies (ULBs). The task has been traditionally assigned to the Pest Control Officer of the Public Health Department. Mumbai was especially vulnerable to the dangers of a plague on account of it being a port city. The city’s infamous plague attack at the end of the 19th century killed 200,000 people. During the plague threat of 1994, Mumbai used the plague vaccine prepared by the Municipal Rat Destruction Unit at the Haffkine Institute to bring the epidemic under control. Wards of the city were divided into ‘rat labour boundaries,’ assigned to beat officers for inspection and prevention. The most common methods for rat destruction were physical and chemical. Additionally, night rat killing was a unique method of rat control that was exclusively used in Mumbai.

During the plague threat of 1994, Mumbai used the plague vaccine prepared by the Municipal Rat Destruction Unit at the Haffkine Institute to bring the epidemic under control.

Delhi, too, has a massive rat population, mainly residing underground, adroitly finding shelter in sewerage networks, water pipes, fibre optic and gas pipelines. Delhi’s rats have thus been able to develop a complex underground network of rat colonies. Kolkata has also been battling rats which have been found to tunnel through the concrete foundations of flyovers and nibble away at vital underground sewage and cable lines. They have been seen in slums, eateries and historical colonial buildings. Kolkata Municipal Corporation has been seeking advice from other ULBs and exploring measures to combat the growing rat population. In Patna, rats were found to have burrowed under the railway platform causing its collapse. The library of Patna University was at one point closed to deal with rats that had taken over a section of the book shelves. Although some cities around the world have claimed to have successfully controlled rodent growth, in most places, rats have managed to survive and continue to operate as usual.

Rat control complexities

Over the years, different rodent management measures have come  into use. Trapping rats has been one of the earliest used methods. Use of rodenticide has also been common. However, rats are known to develop a resistance to them. The use of rat poison has not been favoured by experts since it often ends up bio-accumulating in the food chain. Encapsulated bait formulations have been observed to have reasonable success. These, however, run the danger of risk to non-target. Chemical control, according to rodentologists, is the most effective known method for rodent management in urban conditions. However, even this has had limited effectiveness.

Urbanisation in countries like India, along with heavy densification of its cities will inexorably lead to conditions that will substantially support the multiplication of rats.

Even though city rats are widely prevalent and pose a huge threat to city infrastructure as well as the health of citizens, they are among the least studied wildlife in urban environments. As a consequence, very little is known about their ecology. This disinterest in rodent research exists despite the broad concession that traditional methods of rat control in the urban landscape have not produced the desired results. The ongoing speed of human urbanisation, compounded by the effects of climate change, is leading to a proliferation of rat-related risks. Further, urbanisation in countries like India, along with heavy densification of its cities will inexorably lead to conditions that will substantially support the multiplication of rats.

Studying urban rats has also been fraught with difficulties because rats inhabit spaces owned by both public and private entities, which poses problems with entry and a hindrance to the prolonged observation of rat behaviour. A suitable urban rat research site, that is a mix of public spaces, commercial and business sites, as well as residential areas, which can allow for a comprehensive study over a long enough period to generate robust science, is difficult to obtain. This problem is directly attributable to some notable knowledge gaps that continue to accrue in the rat ecological literature.

However, there have been recent successes achieved in fertility control studies through immuno-contraceptives. What is now required is testing their effectiveness in a live situation. Here, NYC has taken the lead by designating city areas where contraceptive delivery will take place. This step towards rodent control could prove invaluable in the cities’ fight against rats. If this experimentation is successful, it may open up a new methodology that can provide an effective mechanism for rodent control globally.


Ramanath Jha is a Distinguished Fellow at the Observer Research Foundation, Mumbai.

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Author

Ramanath Jha

Ramanath Jha

Dr. Ramanath Jha is Distinguished Fellow at Observer Research Foundation, Mumbai. He works on urbanisation — urban sustainability, urban governance and urban planning. Dr. Jha belongs ...

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