6. LIFE CYCLE 3- Another sandfly bites human and ingests blood infected with Leishmania 2- Sandfly bites human and injects Leishmania into skin 1- Sandfly bites animal and ingests blood infected with Leishmania 4- Cycle continues when sandfly bites another human or animal reservoir
Highlighted areas are parts of the world where leishmaniasis has been reported. Taken from British Medical Journal 2003 326:378
Data on leishmaniasis is based on voluntary reporting by countries so true incidence may be higher in countries that are not likely to report. Numbers of cases in Iraq come from recent Promed messages (authors Desjeux and Deresinki)
Reservoir: Small animals – including dogs, rats, gerbils, sloths. Vector: Sandflies which become infected by ingesting blood from these small animals. The sandfly is very small and does not make noise when it flies. They are most active at night (from dusk to dawn) and less active during the hottest part of the day. About 1/3 the size of a mosquito, they can fly through the mesh of mosquito nets unless the bed nets are treated with Permethrin. Their mouthparts are too small, however, to bite through clothing. Lifecycle: Leishmaniasis is spread to humans by the bite of some types of sand flies. Sand flies become infected by biting an infected animal (for example, a rodent or dog) or person. When the sandfly bites an infected animal it ingests blood (specifically white blood cells) infected with Leishmania. The Leishmania changes form inside the gut of the sandfly – from amastigote to promastigote. At night, the sandflies slip through untreated bed nets or land on skin without repellent and bite. Leishmania from the gut of the sandfly are are injected into the skin of the human. In the human the Leishmania again change form – back to amastigote. If another sandfly bites the infected human, the sandfly ingests blood infected with Leishmania , becomes infected, and flys off to infect another human or animal. The life cycle continues. Leishmaniasis also can be spread by blood transfusions or contaminated needles.
Photograph provided by COL Naomi Aronson
Photograph provided by COL Naomi Aronson
Some sores are covered by a scab or have not yet ulcerated so they may look like red raised plaques- sometimes with dry crust/scale
Small, raised lesion on trunk without significant oozing or scab. Photograph provided by COL Naomi Aronson
Multiple lesions on arm with a variety of appearances. Photograph provided by COL Naomi Aronson
Both lesions are leishmaniasis Note the raised border and wet appearance of the sore on the back of the hand. Sores over joints are very concerning as scarring with healing can lead to limited movement of joint. Photograph provided by COL Charles Oster
Back of hand. Note raised border and wet appearance. Patient has bacitracin ointment applied to lesion. Photograph provided by COL Naomi Aronson
Upper Eyelid. Note the dry, crusted/scabbed appearance which is different than previous sores shown. Photograph provided by COL Naomi Aronson
Close up of another dry, crusted lesion with concentric surrounding scale. This is a typical appearance for Old World Leishmaniasis. Photograph provided by COL Charles Oster
Three lesions on face. Raised and dry but not scabbed. Another different presentation. This was Leishmania tropica . Photograph provided by COL Charles Oster
Two children with visceral leishmaniasis. The size of the spleen is marked on the abdomen. Normally the spleen does not protrude below the bottom rib. Photograph provided by COL Charles Oster
Based on our experience with Desert Storm, well nourished American soldiers generally have a less symptomatic, relatively oligoparasitic infection that was not life threatening but posed some diagnostic challenges
Summary of the presenting symptoms of eight soldiers with visceral leishmaniasis from Desert Storm. The summary is from an New England Journal of Medicine article by COL Alan Magill and others from the Walter Reed Army Medical Center Infectious Disease Service.
From the Desert Storm experience, would also consider visceral leishmaniasis in patients with low grade elevated temperature, chronically elevated liver function tests and mild anemia
Much of the destruction is from a hyperimmune reaction to the Leishmania infection. There are not many parasites in the affected tissue so confirming the diagnosis can be difficult. This form of leishmaniasis would be unusual in soldiers infected in South West Asia.
Photograph provided courtesy of COL Donald Skillman
Sandflies bite dusk to dawn so personal protection is most important during these times. Even light clothing covering skin is sufficient to prevent the bite of the sandfly. DEET is the most effective insect repellent. Sandflies are small enough to fly through bed netting unless it is treated with permethrin.
On occasion, a deep scraping of a skin lesion can be sufficient when the tissue scraping is subjected to giemsa stain, Leishmania culture and/or PCR.
Methods available in the US for antibody detection in the serum - IFA test - rk39 dipstick (Kalazar Detect TM )
For expert second level review, slides of potential leishmaniasis cases can be forwarded to Armed Forces Institute of Pathology, AFIP, Geographic Pathology Division, Washington DC Patient may be referred to Walter Reed Army Medical Center for assistance with diagnosis.
Since L tropica is of more concern in the SWA theatre (because of potential visceralizing infection, rare mucocutaneous involvement, and chronic (recidivans) skin infection) , would not advocate use of azoles routinely as there is not data to support their use in L.tropica and speciation can not be reliably made using clinical appearance. Mucocutaneous infection is treated with a longer treatment course (28 days)
It is not known what species of visceral leishmaniasis is present in Iraq – WHO reports that children have L. infantum. During Desert Storm some of American soldiers were found to have visceral infection with L. tropica . Published studies of liposomal amphotericin for visceral leishmaniasis have not included patients with L. tropica so it is not known for sure that it would be effective but it is expected likely.
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