Environmental Engineering Reference
In-Depth Information
Malaria is a caused by parasites of the species
Plasmodium
that are spread
from person to person through the bites of infected mosquitoes. The common first
symptoms — fever, headache, chills, and vomiting — appear 10 to 15 days after
a person is infected. If not treated promptly with effective medicines, malaria
can cause severe illness that is often fatal. There are four types of human
malaria —
Plasmodium falciparum
,
P. vivax
,
P. malariae
,and
P. ovale
.
P. fal-
ciparum
and
P. vivax
are the most common.
P. falciparum
is by far the most
deadly type of malaria infection.
39
Environmental factors directly influence malaria transmission. These include
rainfall patterns, proximity of mosquito breeding sites to human settlements,
the distribution and biting patterns of mosquito species, and mass application of
commercial poisons. Changes in weather and climate, as well as natural disasters,
can lead to epidemics of malaria, even in areas where few human cases have been
reported. In the United States, most cases are a result of returning travelers from
malaria-endemic areas. Cases of malaria transmitted through blood transfusions
have also been reported in the United States.
40
,
41
The WHO defines the main objective of malaria vector control as: “to sig-
nificantly reduce both the number and rate of parasite infection and clinical
malaria by controlling the malaria-bearing mosquito and thereby reducing and/or
interrupting transmission”.
39
The two main recommended strategies for limiting
mosquito bites are indoor residual spraying of long-acting insecticide (IRS) and
long-lasting insecticidal nets (LLINs). Larval control and environmental control
of mosquito breeding locations is achieved through a process called Integrated
Vector Management (IVM).
Plague
Plague is a rare but frequently fatally zoonosis caused by the
gram-negative bacterium
Yersinia pestis
. Humans are infected by the bites of
infected rodent fleas, by handling infected animals, or rarely, by human-to-human
transmission of pneumonic plague. Plague was first described in the United
States in 1900 and is thought to have been introduced into San Francisco
from plague-endemic regions of Asia.
42
Plague is now endemic in the western
United States, where a median of seven human cases occur annually.
43
Plague
is enzootic in wild rodent populations in rural areas of the Americas, Africa,
and Asia, with occasional outbreaks among rats or other rodent hosts in villages
and small towns. Wild rodent plague poses a real, although limited, risk to
humans. When infection spreads to rats in urban or populated areas, persons are
at markedly increased risk of exposure. In recent decades, urban outbreaks have
been rare and limited in size.
44
There are three principal clinical forms of plague: bubonic, septicemic, and
pneumonic.
45
All three forms may be accompanied by fever and systemic mani-
festations of gram-negative sepsis and cause high mortality unless promptly diag-
nosed and treated. Patients with bubonic plague have a characteristic bubo (i.e.
one or more enlarged, tender, regional lymph nodes, often auxiliary or inguinal).
Septicemic plague may be primary when the bacteria invade and multiply in the
bloodstream in the absence of an apparent bubo, or may occur secondarily to
