Petfood: how to prevent insect infestation
Insect contamination of petfoods is a potential problem in tropical countries; this paper offers an overview of the situation and how the risks can be minimized.
Pet foods are prone to insect infestation during manufacture and storage unless good protocols are in place to prevent this from happening.
The key areas to focus on in order to prevent infestation are minimizing all potential access to the food, and optimizing the storage facilities.
When considering the quality of a petfood, the first thing that comes to mind is the resulting product of the combination of ingredients and how they are formulated. However, it is important to remember that other aspects are involved, such as the various stages of the manufacturing and distribution process. Maintaining the organoleptic characteristics of a product (i.e., aspects of the food that create an individual’s experience of it, via smell, sight and taste) along with its nutritional value, from manufacturing and storage to the point of consumption by the dog or cat, is currently one of the greatest challenges faced by the pet food industry. Reputable manufacturers have quality control measures to prevent insect infestation.
When failures occur during this process, both the owner and their pet are affected, and complaints regarding deviation from the product standard when an owner opens their petfood are becoming increasingly common. In warmer countries in particular, the most frequent grievances are those related to insect infestations. Owners are particularly sensitive to these issues, and while the industry invests significant resources in order to prevent pest infestation during manufacture 1, failures in relation to quality control in the final distribution chain, and how this is often directly related to complaints, is widely recognized.
In almost all cases where insect contamination occurs, this is not in the manufacturing plant but further down the chain, usually during storage in a distribution warehouse or at point of sale.
Main insect pests
The insect that most commonly infests pet food in warmer countries is Necrobia rufipes, the red-legged ham beetle. This is a commonly found flying pest that feeds on protein-rich foods 2 and can therefore cause significant damage to stored products. The adult insect is greenish blue in color and measures between 3.5-7 mm (.14-.28 inches) in length (Figure 1). Depending on the temperature and the availability of food, the life cycle can vary from 36-150 days or more 3 and has a complete metamorphosis (i.e., egg, larva, pupa and finally the adult insect (Figure 2)). The larval form seeks a dark environment, and at the end of this stage it will seek a dark, dry place in which to build the cocoon, which can be completed in 24 hours (Figure 3). The pupal cocoon is formed by filling the open sides of the crevice chosen by the larva with a white substance produced in the larva’s mouth in the form of frothy droplets 4. It is not known if the adult N. rufipes can penetrate closed (i.e., rather than damaged) food packaging 5 (Figure 4).
Other insects frequently found in stored food include Lasioderma serricorne (the cigarette beetle), Tribolium castaneum (the red flour beetle) and Plodia interpunctella (the Indianmeal moth).
Factors affecting infestation
The four factors necessary to permit development of an insect infestation are access, harborage (= storage area), food and water. However, since production and storage of dog and cat food implies availability of both water and food, it is necessary to focus on preventing the insect’s potential access to the food and harborage in order to avoid contamination. This approach must be implemented throughout the manufacture and supply chain; if the insect cannot find either food or harborage, it will not live near the stored product.
In terms of access, the challenge is to ensure the integrity of the stored products. In order to do so, pet food packages should be kept away from sunlight and heat. Products must not be stored directly on the floor or on wooden pallets, and should be handled properly. This includes avoiding pulling the packages by the welds, and ensuring that packaging is not punctured. Furthermore, anything in the storage area that does not serve a purpose, such as plastic materials, cardboard boxes or old pallets, should be removed.
How infestations occur
As noted above, the lack of good storage and product handling practices are a risk factor for infestations when insects are present in the environment. Large volumes of stock and low stock rotation can facilitate infestations, and although these can occur at any point in the production chain, they are most likely to occur at a point of sale.
Additionally, climate and seasonality have a considerable impact, predominantly in tropical countries and during the hottest and most humid seasons, during which high temperatures and humidity levels form the perfect environment for significant infestations.
Harm to pets’ health and the role of the veterinarian
Ingestion of an adult insect may give rise to an effect comparable to that of ingestion of a foreign body, but the size of the animal and the number of larvae/insects consumed must be taken into account. It is probably more important to remember that insects and pests can be vectors for the transmission of microorganisms (such as cross contamination by bacteria such as Salmonella spp. and E. coli) from an infested place to the pet food. Everyone involved in each stage of the process therefore has a significant responsibility to ensure that the risk of infestation is minimized. This includes the veterinarian, as he or she often guides an owner when discussing pet food, and especially if a product has been found to have been attacked by insects.
Adequate pest control by a specialist company is required during manufacture, transport and storage of pet foods; the company must analyze the risks of infestation and develop a program with an adequate frequency of visits to facilitate pest monitoring and control. When implemented in unison, all these suggestions will yield good results.
The lack of good storage and product handling practices are a risk factor for infestations when insects are present in the environment.
It is also important that the veterinarian is proactive and advises owners as to how to minimize any risk of insect contamination, as follows:
- When purchasing the product in the store, check that the packaging is intact, with no holes or other damage – be wary if there are insects where the petfood is stored and displayed for sale;
- Store food at home in a dry, ventilated place and in appropriate containers. Avoid keeping the food on the floor or close to walls;
- When offering food to their pet, place the calculated amount in the feeder and prevent spillage onto the floor;
- Remove the food if the animal does not consume the entire amount offered;
- Regularly clean the animal’s feeder and water dish.
When pests are found inside food packaging, it is recommended to instruct the owner to contact the consumer department at the manufacturing company, so that appropriate instructions for disposal and possible exchange can be given. This may also help identify at which point in the chain there was likely contamination, thus contributing to identification of where improvement can be made.
The responsibility for maintaining the quality of a pet food is distributed throughout the supply chain, and as veterinarians we have the chance to change the current narrative by sharing this knowledge with owners, thus contributing directly to building a better world for pets.
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Lambkin TA, Khatoon N., 1990. Culture methods for Necrobia rufipes (De Geer) and Dermestes maculatus De Geer (Coleoptera: Cleridae and Dermestidae). J. Stored Prod. Res. 1990;26;59-60.
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Savoldelli S, Jucker C, Peri E, et al. Necrobia rufipes (De Geer) infestation in pet food packaging and setup of a monitoring trap. Insects 2020;11(9);623.