Wild rodent infestations can destroy crops and pose many risks to public health. According to the CDC, they are hosts to many diseases including Hantavirus, Monkeypox, Salmonella, Hemorrhagic fever, Lassa fever, Leptospirosis, Arenavirus, Sylvatic Typhus, and Tularemia. Wild rodents may also indirectly spread diseases to humans and other animals through infected ticks, mites, mosquitoes, and fleas that feast on them. Such indirect illnesses include Lyme disease, Plague, Typhus, Colorado Tick fever, Anaplasmosis, Cutaneous leishmaniasis, Rickettsialpox, among several others.
Efforts to control wild rodent populations include removing sources of food and water as well as objects or spaces they can hide in. Infestations may require trapping, rodenticides, or bringing in natural predators such as cats and owls. Anticoagulant rodenticides, which cause internal bleeding, have been outlawed in certain regions because of the risk they pose to other animals, predators, pets, and even small children. Treatment of accidental overdose typically includes administering vitamin K, which is important in the blood clotting process.
Malaysian wood rats (Rattus tiomanicus), pictured above, are a common concern in oil palm plantations as they are known to eat young palms. They also consume palm fruits and reduce the amount of oil that can be extracted from the plant. Because these rats reproduce quickly, populations can rapidly spiral out of control. The goal of farmers is to control the population of rats and limit their damage to just the fresh fruit. Control measures used at these plantations typically include rodenticides (such as anticoagulants) and owls.
In attempt to reduce harm to barn owls, researchers in Malaysia tested the use of cholecalciferol (also known as vitamin D3) as an alternative rodenticide in oil palm plantations. Cholecalciferol was first used as a rodenticide to control house rats in the 1980’s. When consumed in high amounts, cholecalciferol increases calcium levels in the blood, leading to calcification of blood vessels and other tissues, as well as loss of appetite. In contrast to other rodenticides, barn owls that consumed wood rats treated with vitamin D3 remained healthy throughout the 6-month observation period and showed no signs of behavioral or physical symptoms. This reduced risk may be unique to owls, however, as cholecalciferol has been shown in other studies to harm dogs, cats, and other mammals that prey on treated rodents.
Sources:
AAM Noh, AH Ahmad, H Salim. Efficacy of cholecalciferol rodenticide to control wood rat, Rattus tiomanicus and its secondary poisoning impact towards barn owl, Tyto javanica javanica. Scientific Reports. 13: 2854, 2023.
National Pesticide Information Center
Categories: Agriculture, Aquaculture, and Livestock, Environment, Urbanization
Tags: Cholecalciferol, oil palm, owl, Palm oil, rat, rodent, vitamin D3
Life Lines by Dr. Dolittle 
