Public costs 1. Cost of health-related conditions

Public Health Significance of Urban Pests 65 The costs of medical problems associated with cockroaches are difficult to estimate. Asthma affects 15 million Americans, approximately a third being under 8 years of age Benson Marano, 1998. Children allergic to cockroach allergen and exposed to high levels had a 3.4 times higher rate of hospitalization for asthma than other children. This group also had 78 more unscheduled visits to health care providers because of asthma. They also missed significantly more days of school than did other children Rust Reierson, 1991. An estimate of the national economic burden of asthma in the United States in 2000 is US 14.5 billion Krieger et al., 2002. The actual medical and societal costs associated with cockroach-related asthma might be a considerable portion of that cost.

2.3.2. Cost of control and management

The costs of cockroach control services vary greatly, depending on the pest species and locality. Because it is generally assumed that cockroach IPM programmes cost more than conventional pest control services, a comparison of conventional programmes with IPM programmes is insightful. In 1998, in the north-eastern United States, conventional pest control services cost US 65 an hour, whereas IPM services were US 80 an hour Rambo, 1998. However, it is assumed that IPM should actually reduce the frequency of visits and consequently the labour costs in the long term. Williams and colleagues 2005 reported that after all costs were considered, conventional service was US 8.57 per unit and IPM was US 7.49 per unit. In their study, cockroach infestations were very low in schools, and costs would probably have increased if they had been more severe. Brenner and colleagues 2003 set up an IPM-based programme for low-income house- holds in New York City, involving monitoring, baiting, cleaning and structural repairs. The costs for IPM were US 46–69 per unit in the first year and US 24 per unit in the following year. In comparison, conventional chemical controls cost US 24–46 per unit and involved no repairs or structural modifications to the apartments. In IPM program- mes, the number of cockroach infestations declined by 50 over six months. In public housing in Portsmouth, Virginia, the costs of conventional crack-and-crevice treatments with sprays and dusts were compared with vacuuming, baits and insect growth regulators IGRs for controlling German cockroaches Miller Meek, 2004. The average costs for IPM and conventional treatments were US 4.06 and US 1.50 per unit, respectively. After eight months, cockroach populations decreased about 80 in IPM units, compared with a 300 increase with conventional treatments. In 2006, in the United States, the cost of treating an apartment was about US 150 and buildings typically cost US 1200 or more to treat. Commercial accounts, such as restau- rants, typically cost US 250 a month to treat.

2.4. Impact of poverty

The physical and sanitary conditions of a dwelling greatly affect the likelihood of coc- kroach infestations, especially of German cockroaches. Bradman and colleagues 2005 Cockroaches 64 decades, and they may spread porcine parvoviruses Tarry Lucas, 1977. In addition, German cockroaches may serve as an important mechanical vector of porcine verotoxi- genic Escherichia coli. As a result, Zurek Schal 2004 recommend the incorporation of cockroach IPM into disease prevention and control programmes in the pig-farming industry. Kopanic and colleagues 1994 reported that American cockroaches collected at feed mills and poultry hatcheries were positive for Salmonella spp., raising concerns about infecting hatched chicks and farm flocks. Fischer and colleagues 2003 reported that nymphs of oriental cockroaches were capable of transmitting paratuberculosis Mycobacterium avium ssp. paratuberculosis and avian tuberculosis Mycobacterium avium ssp. avium in their faeces. Isolates from the cockroaches and their faeces were virulent to chickens. American cockroaches, feeding on the faecal matter of opossums that carried Sarcocystis falcatula , were potential carriers to non-American psittacine birds, especially cockatoos and cockatiels. The birds contracted the disease by either eating infected cockroaches or possibly contaminated food Clubb Frenkel, 1992. Even though numerous studies have demonstrated the ability of cockroaches to pick up and later excrete or transfer pathogens, definitive evidence that cockroaches are vectors for human disease is still lacking. However, the prevalence of cockroaches near human and animal wastes, human food, and human environments creates sufficient concern about their role as vectors. This potential health threat necessitates the control of coc- kroaches in food handling areas, hospitals, animal-rearing facilities, zoos and human resi- dences. The incidence of cockroaches in commercial food-handling establishments exceeds 50. In New York City, 53 of the 18 000 food establishments inspected in 1976 had insect infestations Dupree, 1977. In a random survey of 100 commercial food-handling esta- blishments in Los Angeles, 62 were infested with German cockroaches. All of them had professional pest control service Rust Reierson, 1991. It is likely that as many as 70 of all food-handling establishments have cockroach infestations. 2.3. Public costs 2.3.1. Cost of health-related conditions In the United States, there were more than 21000 pest control companies in 1997, with an estimated annual income of US 4.5 billion. Some 300000 retail food outlets, 500000 commercial restaurants and kitchens, and 70000 hotels and motels were under service contract Potter Bessin, 1998. In 2004, some 19000 pest control companies generated US 6.5 billion – a 6 increase over revenue generated in 2003 Curl, 2004. The impor- tance of cockroaches for the pest control industry in the United States has declined in recent years, but cockroaches still represent 22 of service sales Anonymous, 2002; Curl, 2004. Possibly US 1 billion are spent on professional services in the United States each year to control cockroaches. Public Health Significance of Urban Pests 67 Building practices, such as hollow-wall voids, drop ceilings and voids under cabinets, attics and built-in appliances, provide suitable harbourage for cockroaches. The elimi- nation of these harbourages is the primary goal of so-called built-in pest control or insect proofing. The use of inorganic dusts to eliminate cockroaches in harbourages and voids has long been advocated and is a successful means of controlling German cockroaches Ebeling, 1975. Inorganic dusts are preferred, because they retain their insecticidal acti- vity as long as the dust deposits remain intact and do not clump or cake. Repellent dusts, such as silica aerogel, are typically applied at the time of construction to prevent coc- kroaches from establishing themselves in wall and sub-cabinet voids. Non-repellent dusts, such as boric acid, are applied to existing infestations to provide remedial control. Non- repellent dust, however, will not scatter existing infestations. Non-repellent dusts should be routinely reapplied when flats are being refurbished to accommodate new occupants. One important advantage of built-in treatments is that the dusts are applied in areas not readily accessible to people and pets. Contrary to common belief, relative humidity does not strongly affect the toxicity of most insecticidal dusts, especially inorganic dusts. In fact, as boric acid dusts and silica aerogel dust plus synergized pyrethrin are wetted, their toxicity actually increases. In many cities throughout Europe and the United States, formerly state-owned and mana- ged housing projects are being converted into privately owned dwellings. These conver- sions present special problems in providing IPM programmes, because of the inability to inspect, monitor and treat all units within a building complex. In these units, inorganic dusts should be reapplied when flats are renovated between occupants. Community action plans and education programmes will be important in implementing IPM under these conditions. Also, cooperation is essential to ensure that all flats are treated.

2.6. IPM of cockroaches