Textbooks have traditionally given the impression that fleas are relatively ‘clean’ and mostly represent a nuisance pest due to their bites. Recent scientific studies, however, show that they are far better at transmitting serious diseases than we previously thought.
Whilst the infamous bubonic plague was spread by fleas, the culprit was the rat flea, Xenopsylla vexabilis (Jordan), a species rarely encountered nowadays. We mostly encounter the cat flea, Ctenocephalides felis (Bouché) which, despite its name, infests a wide range of animal species, including dogs and rodents. Very occasionally we might meet the dog flea, Ctenocephalides canis (Curtis).
Recent developments in our knowledge of murine typhus (Rickettsia mooseri) have shown the importance of cat fleas in its transmission. Whilst it resembles a milder form of epidemic typhus, about one in 20 people infected with murine typhus will die from it. We now also know that R. mooseri can cross into developing eggs, meaning larvae hatching from infected eggs are potential sources of infection as well as the adult fleas.
Murine typhus is reported all over Australia, but is particularly prevalent in tropical and sub-tropical coastal areas where rodents are commonly found. Murine typhus infections may also be caused by inhalation of airborne infected flea faeces. Professional pest managers should always wear protective masks when dealing with areas heavily infested by rodents or fleas to reduce the risk of murine typhus from inhaled dust.
Cat fleas are the primary vector of cat scratch fever (Bartonella henselae) with the spread of the bacteria occurring when flea faeces are scratched into bites or wounds. They also are one of the hosts of the double-pore dog tapeworm, Dipylidium caninum. This tapeworm is a parasite of dogs and cats, but it can infect children, with the immature stage of the tapeworm developing in the intestine of the child. Whilst it does not cause obvious symptoms and is not a cause of serious disease, it is of concern. The most obvious sign of infection is finding a stage of the tapeworm, known as a proglottid, in a child’s bowel movement. A proglottid is whitish, about the size and shape of a pumpkin seed, and capable of undulating movements.
The prevalence of flea infestations can be related to their biology. Cat fleas are amazingly well adapted to securing large, moving hosts. They have a jumping speed of 3.6m/s, and a jumping height of 15-17cm.
In Australia, larvae survive outdoors all year round. In the summer months, eggs develop into adults in 20–24 days, whereas in the winter it typically takes 36–50 days. Immature stages even survive frosts in protected microhabitats.
Of note for flea control programs, some adults emerge as late as 155 days after egg deposition, clearly showing the importance of the pupal and pre-emerged adult stage in surviving adverse conditions. Pest managers need to account for this in developing their control strategies. Regional director for Ensystex, Steve Broadbent, said, “Flea control is an increasingly demanding business and, with concerns over resistance due to widespread use of insecticides by the public on animals, product selection is important.
“To ensure the long-term success of flea control programs and avoid callbacks, pest managers need to be thorough in their approach. Where domestic animals remain at the property, the owners must be advised to seek veterinary advice on appropriate flea prevention measures. Infested items of animal bedding are also best destroyed.
“When it comes to the treatment of the property and the grounds, this is when the professional can excel by hitting all the flea life stages to ensure population elimination.”
Taking a dual approach
Bithor Dual Action is an adulticide flea treatment with a unique dual mode of action and long-term residual performance. It is a blend of two residual insecticides, each with a different mode of action, from two different chemical groups: bifenthrin (a Group 3A pyrethroid) and imidacloprid (a Group 4A neotenic).
“Bithor eliminates the toughest pests, including resistant strains, which is why it should form the core of your flea control strategy,” advised Mr Broadbent. “Each active potentiates the other to provide outstanding results. Bithor Dual Action can be used indoors or outdoors, and is suitable for most applications since it is non-repellent, water-based, odourless, non-staining and has a broad spectrum of pests approved on the label.”
Mr Broadbent added that when it comes to fleas, it is a good idea for pest managers to also take account of the eggs and late-emerging larvae. “We recommend that Bithor Dual Action is tank-mixed with Exothor Insect Growth Regulator to give a boost to your flea elimination program.
Exothor inhibits the formation of N–acetylglucosamine, leading to reduced levels of chitin in the insect’s cuticle, leading to abortive moulting.
“Exothor causes the flea larvae to die before pupation and adult emergence, which offers improved long-term elimination. Exothor also stops normal embryonic development and has been shown to be effective at stopping development of all three flea larval instar stages.”