Public Health Significance of Urban Pests
135
Gbakima and colleagues 2002 reported a very high prevalence of both common and tro- pical bedbugs up to 98 of rooms infested in camps for internally displaced persons in
Freetown, Sierra Leone. In Australia, a government public health agency reported a 400 increase in bedbug complaints submitted during 2001–2004, compared with
1997–2000. They also reported increased interceptions of bedbugs mainly in luggage by national quarantine inspectors from 1986 to 2003, with 74 of those occurring from 1999
to 2003 Doggett, Geary Russell, 2004.
4.2.4. Other species of Cimicidae that can affect people
Besides the common bedbug, two other species of bugs in the family Cimicidae are synan- thropic ecologically associated with people and historically well-known and significant
pests of people in certain geographical regions. Those are the tropical bedbug species, C. hemipterus
, which is distributed throughout the tropics, and Leptocimex boueti, which is limited to tropical western Africa.
Several other species of the Cimicidae, such as the European swallow bug Oeciacushirun- dinis
, frequently enter human dwellings and feed on people opportunistically, especially when their normal hosts are eliminated or depart on normal natural migrations. The eas-
tern bat bug Cimex adjunctus, which feeds on several species of bats and is distributed mainly east of the Rocky Mountains in North America, frequently invades human dwel-
lings and readily feeds on people. The cliff swallow bug Oeciacus vicarius, which lives in the nests of cliff swallows Petrochelidon pyrrhonota and is distributed throughout the
nearctic region that is, the biogeographic region that includes the Arctic and temperate areas of North America and Greenland, will sometimes bite people when its hosts are
removed or leave on annual migrations, or when people disturb these bugs in their habi- tat. The European swallow bug, which is associated with house martins Delicon urbica
and is distributed throughout northern Africa, most of Europe and Turkey, will some- times enter human dwellings and feed on people. The poultry bug or Mexican chicken
bug, Haematosiphon inodorus, will readily feed on people in Mexico and the south-wes- tern United States, but it is most commonly found associated with poultry nests and the
nests of large raptors, such as hawks and eagles. The chimney swift bug Cimexopsisnyc- talis
, which lives in the nests of Chimney swifts Chaetura pelagica, is distributed throu- ghout most of the eastern United States and has occasionally bitten people.
There are at least four species of bat bugs in the species group with Cimex pipistrelli. They collectively occur throughout most of Europe and feed mainly on local species of bats.
These and other species in the C. pipistrelli group occasionally invade human dwellings, and one or more species have been reported to occasionally feed on people. The taxono-
mic status of this species group is presently somewhat unclear.
The western bat bug, Cimex pilosellus, which feeds on several species of bats and is found almost exclusively west of the Rocky Mountains in North America, has been repeatedly
reported to invade human living spaces, but there are no confirmed reports of this spe- cies actually biting a person. Because multiple species of the Cimicidae can potentially
occur in human dwellings, precise and careful identification is critical for proper imple-
Bedbugs
134
4.2. Resurgence of bedbug populations in Europe and North America
4.2.1. Evidence of resurgence in N orth America
In 1997, in the United States, reports of bedbug and specimens submitted for identifica- tion to the National Pest Management Association NPMA were limited to two separate
infestations in two states. By September 2001, such submissions totalled 29 infestations in 18 states and the District of Columbia. By April 2004, bedbugs in samples submitted for
identification had come from a total of 108 infestations in 4 Canadian provinces, 3 states of Mexico and 40 states in the United States. Also, public or media inquiries to the
NPMA about bedbugs have gone from only 1 in 1997 to at least 14 in 2001and to more than 100 in 2005. Many pest management companies in the United States have seen major
increases in services for bedbug infestations over the past few years Krueger, 2000; Cooper Harlan, 2004; Potter, 2004; Gooch, 2005. For example, one small company
went from two unusual infestations in 2001 to an average of a call a day Johnson, 2005. Also, a national company had an increase of 300 in bed bug control calls from 2000 to
2001, another 70 increase in 2002 and another 70 increase in 2003 F. Meek, Orkin Pest Control, Atlanta, GA, personal communication, June 2005. Moreover, one small
company, which formerly specialized in termite control, reported that more than 25 of its profit for 2004 came from bedbug treatments Johnson, 2005. Resources invested by
the NPMA, manufacturers, suppliers and individual pest management companies to train PMPs in bedbug management have increased greatly in the past two years Cooper
Harlan, 2004; Potter, 2004; Gooch, 2005; Johnson, 2005. Furthermore, between the beginning and end of 2003, public health officials in Toronto, Canada, reported a 100
increase in phone complaints about bedbugs, a 100 increase in the number of com- mercial treatments for bedbugs in private residences and a more than 50 increased inci-
dence of bedbugs in public shelters Hwang et al., 2005.
4.2.2. Evidence of resurgence in Europe
In Europe, no precise data were available to document quantitatively the resurgence of the common bedbug. Nevertheless, observational reports from Germany and the United
Kingdom claim a sharp increase in the frequency of infestations during the last decade. In the city of Berlin, Germany, more than a tenfold increase in the frequency of bedbug
infestations has been reported, rising from five cases reported in the 1992 to 62 cases in 2002 and to 76 cases in 2004 Bauer-Dubau, 2004. In the case of Berlin, the three major
reasons for bedbug infestations are considered to be:
1. purchases of used furniture and electronic devices, 2. business travel,
3. holiday travel.
4.2.3. Resurgence in other parts of the world
Similar trends in resurgence have been occurring in several countries on other continents.
Public Health Significance of Urban Pests
137
4.3.2. Potential as vectors of human pathogens
Common bedbugs have been found to naturally contain 28 human pathogens, but they have never been proven to transmit biologically or mechanically even one human patho-
gen Usinger, 1966; Burton, 1968 – specifically hepatitis C Silverman et al., 2001 and HIV Webb et al., 1989. Nevertheless, shedding of viral DNA fragments in faecal mat-
ter and transstadial across life stage transmission of hepatitis B virus seem to support the possibility of mechanical transmission by contaminated faeces, or when bugs are crus-
hed during feeding onto abraded skin by a susceptible person Jupp et al., 1991; Blow et al., 2001. The study by Jupp and colleagues 1991 clearly indicated that common bed-
bugs do not biologically transmit hepatitis B. Also, it is still unclear whether or not the reported induction of skin papillomas in the European rabbit Oryctolaguscuniculus sub-
sequent to continuous exposure to bites of common bedbugs irradiated by gamma rays el-Mofty, Sakr Younis, 1989 is caused by a viral pathogen.
One species of Cimicidae, the cliff swallow bug so far, found occurring naturally infec- ted, only in western North America, has been proven to transmit at least two identifia-
ble virus entities in the western equine encephalitis complex: these are the Fort Morgan virus FMV and a distinct strain of FMV, called Buggy Creek virus Hayes et al., 1977;
Calisher et al., 1980; Brown Brown, 2005. Transmission has thus far only been repor- ted to occur from infected swallow bugs, mainly adult bugs that usually live in or on the
swallows’ nests over the winter until the next year’s susceptible hatchlings of cliff swal- lows. So far, no risk to people from this epizootic virus cycle has been established. The
bugs are not very mobile and tend to stay at, on or in the swallow nests and do not rea- dily move to a different nest that is more than a short distance away Foster Olkowski,
1968. A few individual bedbugs of this species have been found very rarely in local small rodent nests and occasionally in a nearby nest of a European or barn swallow Hirundo
rustica
. This species has been reported to have fed on a person, and it readily feeds on mice in laboratories Usinger, 1966. Although some species of the Cimicidae that seek
human beings over other animals have not been investigated very thoroughly, it is unli- kely that any of them pose a threat as a human pathogen vector.
In Europe, infestations of human dwellings by the European swallow bug often occur, especially during the wintertime, when their normal hosts have migrated to Africa.
Abandoned swallow nests may harbour hundreds of overwintering swallow bugs that search for blood hosts during warmer winter weather conditions. Within a radius of up
to 5m, swallow bugs may infest buildings through any opening, and they feed readily on people. In an extensive study in Colorado, cliff swallows and house sparrows Passer
domesticus
, which live within the swallow nesting colonies, were the main vertebrate hosts for maintenance and amplification of FMV. However, the presence of fairly large
populations of these bugs, and their transmission of FMV, reportedly had no significant impact on the health or reproduction of local populations of cliff swallows, house spar-
rows or barn swallows in co-located or adjacent breeding sites Scott, Bowen Monath, 1984.
Bedbugs
136
mentation of pest control measures. Although it is rare that they attack people, these spe- cies are noted because infestation of human dwellings may occur.
4.2.5. Future prospects