Leprosy (Hansen Disease) is a chronic, systemic infection.

• Mycobacterium leprae infects the skin and peripheral nerves, deformities due to lack of pain sensation.

• Disfigures skin and bones, twisting limbs and causing claw hands.

• 2600 year old disfiguring disease has finally met it’s match with multidrug therapy.

Figure 24A: Boy with

leprosy before treatment

Courtesy of American Leprosy Mission, 1 ALM Way Greenville, SC 29601

Figure 24B: Boy with leprosy

after treatment

– Influenza A strikes every year and causes most epidemics.

– Influenza B also strikes every year but is less common than type A.

– Influenza C causes a mild respiratory illness but not epidemics.

Figure MF02: Preschoolers drive flu outbreaks

© Cristina Fumi/ShutterStock, Inc.

– Shingles is an adult disease caused by the same virus as chickenpox.• After infection, VZV can remain in nerve cells for many

years.• If they are reactivated, they can travel to the body

trunk and cause blisters and patches of red.• It can also cause facial paralysis and severe “ice-pick”

pains.• It can occur repeatedly.• Postherpetic neuralgia is the persistence of shingles

pain for years after the blisters have disappeared.• Zostavax is a vaccination to prevent Shingles.

– Polioviruses multiply in:• tonsils.• lymph tissue.• gastrointestinal tract.

– Sometimes the viruses pass through the bloodstream to the meninges.

• This can result in paralysis of limbs and trunk. – In bulbar polio, the viruses infect the medulla, affecting

nerves in the:• neck.• face.• upper torso.

– Trivalent vaccines contain all 3 types of poliovirus.– Postpolio syndrome occurs in individuals who had the

disease decades ago.

– Excessive antibiotic use may decrease protective bacteria in the vagina and intestine, allowing C. albicans to flourish.

– Oral candidiasis (thrush) involveswhite curd-like growth on the mucous membranes of the mouth.

– Onychia involves hardening, browning, and distortion of fingernails.

Figure 21B: Oral candidiasisCourtesy of CDC

• Pneumocystis pneumonia (PCP) can cause a lethal pneumonia.– It is caused by Pneumocystis jiroveci.

– It is a common infection in AIDS patients.

– P. jiroveci has a complex life cycle in the alveoli.

– It is usually transmitted through respiratory droplets.

• Other fungi also cause mycoses.– In aspergillosis, conidia enter the body and grow as a

mycelium.• It is commonly caused by Aspergillus fumigatus.

• Surgery may be necessary to remove an aspergilloma from the lungs.

• Aspergillus can also cause otomycosis in earwax.

• Disseminated Aspergillus can affect the heart.

• Several protozoal parasites cause diseases of the digestive system.– Amoebiasis is the second leading cause of death

from parasitic disease caused by Entameoba histolytica.

– Cysts enter the body through food or water contaminated with feces.

– Trophozoites emerge in the intestines, causing loose stools, stomach cramping and pain.

– Lesions may form, causing amoebic dysentery with pain, bloody stools, and fever.

– Rarely, parasites can spread to other organs and cause fatal abscesses.

18.3 Protozoal Diseases of the Blood and Nervous System

• The Plasmodium parasite infects the blood.– Malaria affects 300-500 million people.

– Four species of Plasmodium cause malaria: • P. vivax• P. ovale• P. malariae• P. falciparum

Figure 01: Malaria Cases (per 100,000) by

Country - 2008

Source: Data from the WHO/Malaria Department.