Health risk and exposure assessment
5.3. Health risk and exposure assessment
Plague, caused by the Gram-negative bacterium Yersinia pestis, is the most significant zoo- nosis that involves fleas. The fleas transfer the bacterial infection among their rodent hosts and to people Gage Kosoy, 2005. A plague infection is characterized by fever, chills, headache and malaise that lead to extreme physical weakness; the symptoms vary, depending on the form of plague. The principal clinical forms include bubonic plague, septicaemic plague and pneumonic plague. Untreated bubonic plague has a case-fatality rate of about 50–60, but current therapies, including treatment with an appropriate course of antibiotics, markedly reduce fatality from it. Untreated primary septicaemic plague and pneumonic plague are invariably fatal. Septicaemic plague and pneumonic plague also respond to early diagnosis and treatment; however, patients who do not receive appropriate therapy for primary pneumonic plague within 18 hours after the onset of symptoms are unlikely to survive. Historically, plague has resulted in considerable human mortality, producing significant population declines along with sociological changes. In the Middle Ages, bubonic plague the so-called Black Death killed between a quarter and a third of Europe’s population within just a few decades Gage Kosoy, 2005. During the last pandemic, between 1896 and 1911, more than seven million people died of plague in India. During the last half of the 20 th century, plague outbreaks were reported in Africa, Asia, and North and South America. Nowadays, the number of annual cases is about 2000–3000 worldwide with more than 90 of them in Africa, with a case fatality rate of about 7 WHO, 2004. The infection obviously remains entrenched in sylvatic rural rodent–flea ecosystems throughout the world, and international travel and transportation make reintroduction and re-emergence likely. Plague rarely occurs in the European Region, but it does occur regularly in North America, with chronic zoonotic mainte- nance of the plague pathogen in the south-western United States provoking ongoing concern. Plague in non-commensal rodents and lagomorphs is dealt with in greater depth in Chapter 13 of this report. The oriental rat flea Xenopsylla cheopis and Xenopsylla brasiliensis are the most impor- tant vectors of plague bacilli, from rat to rat and from rat to human. In the laboratory, other flea species, such as the northern rat flea Nosopsyllus fasciatus, cat and dog fleas Ctenocephalides felis and Ctenocephalides canis, respectively, and the human flea Pulex irritans , have been shown to be capable of transmitting the plague organism, so they may play some role in disease maintenance Traub, 1983. In the American Southwest, ani- mals such as ground squirrels Spermophilusspp. and chipmunks Tamias spp. are reser- voirs of sylvatic plague plague in wild rodents, and rodent fleas play an important role in its maintenance and transmission Davis et al., 2002. The risk of people becoming infected is greatest in urban–rural interfaces, parks and recreation areas, because these are areas where people are most likely to encounter infected hosts and their fleas. The other flea-borne disease of significance is murine typhus, an endemic zoonosis cau- sed by an obligate intracellular bacterium, Rickettsia typhi Azad, 1990. Murine typhus is Fleas 158 flea faeces in their environment. Being negatively phototactic moving away from light sources and positively geotropic burrowing, flea larvae avoid sunlight and actively move deep into carpet or under organic debris. Larvae typically require 5–11 days to com- plete their three instars, but the larval developmental period may be extended up to three weeks, depending on food availability and climatic conditions Silverman, Rust Reierson, 1981. Because flea larvae are highly susceptible to desiccation, the larval environment is defi- ned by relative humidities over 50; larvae maintained in soil with low moisture fail to develop Silverman, Rust Reierson, 1981. Due to their susceptibility to heat and desic- cation, flea larvae cannot survive outdoors in areas exposed to the sun. Flea hosts prefer shaded areas, so flea eggs are more likely to be deposited in shade, with the resulting flea larvae developing where the ground is shaded and moist. Similarly, flea larvae are pro- tected under the carpet canopy in indoor habitats, where air movement is minimized and humidity is highest. The third instar larva secretes silk and spins a cocoon within which it pupates. Because the silk is sticky, debris from the environment adheres to it, camouflaging the cocoon as a lint ball or dirt clod. The cocoon is ovoid and about 3 mm long. Inside its cocoon, the larva molts to a pupa and the pupa then molts to an adult. The length of residence within the cocoon varies. Under conducive conditions around 27°C and 80 relative humidity, the adult flea may emerge five days after the cocoon is formed, while under adverse environmental conditions or absence of a host the adult fleas may not emerge for many months perhaps over a year. Typically, fleas emerge within two weeks following cocoon formation. After the adult develops inside the cocoon, a stimulus is required to cause the flea to emerge. Such stimuli as movement, heat and carbon dioxide signal the flea that a potential host is nearby, triggering emergence from the cocoon. The pre-emerged adult flea inside the cocoon is more resistant to desiccation than are eggs and larvae Rust Dryden, 1997. Using its rudimentary eyes, the newly emerged flea orients itself towards a potential host by cueing in on movement. Extending its tarsal hooks, the flea leaps towards the host. If it lands on the host, the hooks permit it to cling. Once an adult cat flea acquires a host, it typically remains on that animal for the duration of its life, with host grooming being the most common mortality factor. Unlike cat fleas, rodent fleas spend the majority of their lives in their host’s nest. Because most rodents are nocturnal, rodent fleas tend to feed in the daytime, after their rodent hosts have returned to the nest and are resting. So rodent flea eggs are found in the host nest, as are most of the developmental life stages. Public Health Significance of Urban Pests 161 In North America, plague has been reported primarily in the West, ranging from south- western Canada to Mexico. Human cases average fewer than 10 a year in North America, a rate that has remained relatively constant since plague was introduced into the Americas in 1899 WHO, 2004. Worldwide, the number of murine typhus cases is low, but because symptoms are non- specific and frequently misdiagnosed, infection is presumed to be much more common than reported Gratz, 2004. In Europe, murine typhus has been reported from Bosnia and H erzegovina, Croatia, the Czech Republic, France, Greece, Italy, Montenegro, Portugal, the Russian Federation, Serbia, Slovakia, Slovenia and Spain, and it is consi- dered likely to be present in most other countries, as well Gratz, 2004.5.5. Economic burden of flea infestations
Parts
» TAP.COM - PUBLIC HEALTH SIGNIFICANCE OF URBAN PESTS - WHO/EUROPE - WORLD ...
» Risk of developing allergic sensitization
» Risk factors for developing asthma
» Public health impact of urban asthma
» Dust sampling Airborne sampling Comparison of various methods of allergen exposure assessment
» Cockroach sensitization and asthma
» Size characteristics of airborne mouse and rat allergens Residential exposures
» Dust mites Studies examining thresholds of exposure relevant to disease
» Cockroaches Rodents Studies examining thresholds of exposure relevant to disease
» Comprehensive avoidance of dust mite allergens Multifaceted primary prevention studies
» Limited avoidance of dust mite allergens
» Targeting housing conditions of high-risk groups
» Smokybrown cockroach American cockroach Oriental cockroach
» Brownbanded cockroach Allergy and asthma overview
» Food contamination and disease transmission
» Cost of control and management
» Impact of poverty Cockroaches
» Public costs 1. Cost of health-related conditions
» IPM of cockroaches Cockroaches
» Baits Cockroach control: pesticide applications
» Alternative strategies Cockroach control: sanitation practices
» Biological control Conclusions Cockroaches
» Origins and natural history Habitats within the home
» Food Limiting factors Distribution in Europe and N orth America
» CEH Distribution in Europe and N orth America
» The building envelope Impact of building construction
» The ventilation and heating system
» Furniture and furnishings Overall effect of the housing environment on health or illness
» Sampling methods Dust mite and allergen inspection and detection methods
» Mechanical solutions Modifying environmental conditions
» Washing Dusting Dry cleaning Vacuuming
» Home disinfectants Electric blankets Bed heaters Freezing
» Sunlight Steam cleaning Cleaning
» Autoclaving Steam cleaning Temperature control
» Barrier fabrics Temperature control
» Habitat modification Carpets Physical control methods
» Soft furnishings Air filters
» Anti-allergy sprays Antimicrobial treatments Dehumidifiers
» Pesticides Building construction Methods of house dust mite control
» Control methods Medical practitioners Other
» Background Biology and bionomics
» Other species of Cimicidae that can affect people
» Evidence of resurgence in N orth America
» Future prospects Resurgence of bedbug populations in Europe and North America
» Importance as pests Economic impact Bites and health effects
» Conducive environmental conditions An integrated approach to bedbug management
» Physical removal Exclusion Physical removal and exclusion
» Inspection Detection Inspection, detection and education
» Heat Cold Controlled atmospheres
» Use of pest management products
» Benchmarks for success in bedbug management Conclusions
» Introduction Flea biology Fleas
» Health risk and exposure assessment
» Cost for control and management
» Cost of health-related conditions
» Flea exclusion and physical removal Pesticide applications for flea control
» Foggers General surface treatments IGRs
» On-animal products Conducive environmental conditions
» Pharaoh ant biology Overview of biology and distribution in Europe and North America
» Health hazards 1. Pharaoh ant infestations: pathogen transmission and contamination
» Pharaoh ant distribution and population monitoring
» Fire ant population assessment and monitoring methods
» Fire ant geographic range and potential expansion Fire ants: stinging incidents
» Fire ants: cost of eradication
» Physical exclusion Residual contact insecticides
» Insecticidal baits Fire ants: cost of health-related issues, control and management
» Efficacy of management practices
» Implementation of fire ant control programmes
» Confirmation. Determine where control is needed.
» Fire ants Emerging problems and policy options
» Introduction Biology and bionomics of filth flies in Europe and North America
» N uisance Health hazards 1. Diseases
» Myiasis Health hazards 1. Diseases
» Pesticide applications for fly control Granular baits
» Fly exclusion practices Crack-and-crevice treatments Biological control
» Ultraviolet light traps Sticky traps Jar or bag traps Window traps
» Attractants Perimeter treatments Fly management
» Togaviridae: genus Alphavirus Viruses
» Orthomyxoviridae: genus Orthomyxovirus Bacteria
» Coxiellaceae Anaplasmataceae Spirochaetaceae Bacteria
» Regular nonsporing Gram-positive rods Mycobacteriaceae
» Microsporidia Babesiidae Eimeriidae Protozoa
» Zoonoses and sapronoses of wild birds in the urban ecosystem
» Monitoring and surveillance Management implications 1. Benchmarks
» Techniques for dispersing birds in cities
» Control of wild and feral birds in urban areas
» Economic impact of wild urban birds on human health and of controlling birds
» Introduction Human body lice
» Biological factors Implications for public health
» Louse infestation in Europe and North America
» Physical removal Pesticides Louse management 1. Inspection and detection
» Socioeconomic influences Conducive environmental conditions
» Benchmarks for lice management
» Introduction Ticks of Europe and North America
» LB in Europe and N orth America
» Geographical distribution Lyme borreliosis
» Public health impact of TBE in Europe
» Geographical distribution Geographical distribution Epizootiology and epidemiology
» HME HGA Crimean-Congo haemorrhagic fever
» Boutonneuse fever Rickettsia helvetica
» Clothing Tick removal Clothing impregnation Vaccination
» Host-centred methods Habitat manipulation and urban design
» Tick and tick-borne disease surveillance IPM
» Public activities Pesticide applications
» Surveillance and management Research
» Other mosquito-borne viral infections that cause encephalitides
» Malaria Mosquitoes as a pest nuisance
» Dengue haemorrhagic fever and yellow fever
» Dirofilariasis The spread of mosquitoes and mosquito-borne pathogens
» National reporting and Mosquitoes
» Mosquito control and management
» Sanitation and water management
» Adulticiding Larviciding Mosquito monitoring
» Use of predators biological control Passive protection
» Genetic control and transgenic mosquitoes
» Feeding Biology of commensal rodents 1. Description and natural history
» Reproduction and life cycle of commensal rodents
» Behaviour relevant to control
» Movement Biology of commensal rodents 1. Description and natural history
» Population growth and socialization of commensal rodents
» Sewers and drains Association with urban infrastructure 1. Rodents in housing
» Case study 1 – rat bites in Philadelphia: identifying the factors contributing to risk
» Zoonoses of mice Public health risks in urban areas
» Case study 2: Fairhill case study
» Tree squirrels Types, distribution and abundance
» Chipmunks Ground squirrels, antelope ground squirrels and prairie dogs
» Hamsters Voles Types, distribution and abundance
» Beavers Types, distribution and abundance
» Rabbits and hares Types, distribution and abundance
» Francisella tularensis Major rodent- and lagomorph-related bacterial and rickettsial agents
» California group viruses primarily La Crosse virus CTF virus
» Yersiniae Major rodent- and lagomorph-related bacterial and rickettsial agents
» Borrelia burgdorferi s.l. Tick-borne relapsing fever borreliae
» Toxoplasma Toxocara Major rodent- and lagomorph-related parasitic agents
» Babesiae Leptospirae Major rodent- and lagomorph-related parasitic agents
» Bartonellae Rat-bite fever agents
» Flying squirrels Ground squirrels and antelope ground squirrels
» Tree squirrels Voles and other microtine rodents
» Chipmunks Disease associations with particular types of rodents
» Beavers Disease associations with particular types of rodents
» Rabbits and hares Old World mice
» Dormice N ew World rats and mice
» Introduction The impacts of anthropogenic transformations
» Risk factors for rodent- and lagomorph-related diseases Public health impact
» Costs, control and management of infestations
» Control and management of non-commensal rodents and rodent-related diseases
» Conclusions Non-commensal rodents and lagomorphs
» EU community-level authorization of technical grade active ingredients
» Acute toxicity The precautionary principle
» The substitution doctrine Special considerations given to children’s health
» Toxicity end-points Pesticide hazard identification
» Long-term effects Pesticide hazard identification
» Insecticide synergists N eonicotinoid insecticides
» Spot applications Primary exposure of non-professional users and secondary exposures
» Inhalation Routes of exposure
» Incidental oral exposure Routes of exposure
» Exposure potential Steps of pre-market risk assessment of pesticides
» Tiered approaches to exposure estimation: a basis for risk assessment
» Mathematical mechanistic models Empirical models Some existing models
» Statistical mathematical models SOPs and exposure scenario types
» Comparing pesticide risks from residential and dietary exposures
» Residential applicator exposure assessment
» Toxicity end-points and MOS Residential applicator exposure
» Future actions and data development
» Identification Establishment of threshold levels
» Inspection Evaluation of effectiveness
» Develop an IPM plan Employment of two or more control measures
» Definitions of IPM An integrated approach to managing urban insects and rodents
» Case study 3 Case study 4 Case study 5
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