Vector Transmitted, Soilborne Diseases, and Waterborne Diseases (Lectures 15-16)

Major bacterial waterborne pathogen(s)

Vibrio cholerae, Legionella pneumophila

Major protist waterborne pathogen(s)

Giardia intestinalis

Cholera pathogen

Gram (-); grows in coastal, marine habitats

Cholera pathogenesis

Caused by the ingestion of contaminated water or food. It attaches itself onto the wall of the small intestine and produces cholera toxin

Symptoms of cholera

Severe diarrhea

Diagnosis of cholera

Presence of V. cholerae cells in feces

Prevention of cholera

Vaccinations available for some strains —> only provides short term immunity

Maintain adequate sewage treatment and safe drinking water

Treatment for cholera

Fluid, electrolyte replacement, and antibiotics (e.g. streptomycin).

Pathogen of Legionellosis

Gram (-), obligate aerobe. Found in lakes, streams, soil.

Pathogenesis of legionellosis

Low concentrations in nature, high in air conditioning. It travels via aerosols and infects the lungs.

Mild infection of legionellosis

Pontiac fever: Self limiting fever and cough.

Severe infection of legionellosis

Pneumonia, immune compromised hosts.

Diagnosis for legionellosis

Cultures from body fluids

Prevention of legionellosis

Improved maintenance of heating/cooling systems, killed by temperatures >63°C and hyper-chlorination.

Treatment for legionellosis

No vaccine available, antibiotics (intravenous erythromycin) used instead.

Pathogen of giardiasis

Flagellated protist, mammalian parasite

Pathogenesis of giardiasis

Ingestion of giardia cysts (shedded in feces of infected animals); ubiquitous in natural waters.

Symptoms of giardiasis

Diarrhea, gas (smells horrible), lasts 1-2 weeks (up to a month).

Diagnosis of giardiasis

Microscopy, immunoassays

Prevention of giardiasis

Water filtration (cysts are resistant to chlorine treatment)

Treatment for giardiasis

Antibiotics, variable effectiveness

Common foodborne diseases that cause food poisoning

Staphlyococcus and clostridium

Common foodborne diseases that cause food infection

Salmonella, Campylobacter, Listeria

Pathogen of straphylococcus aureus

Gram-positive, facultative aerobe

Sources/exposure to straphylococcus aureus

Meat, poultry, cream-filled desserts

Pathogenesis of straphylococcus aureus

Enterotoxins, variable among strains and heat-stable

Pathogen for chlostridium spp.

Gram-positive, anaerobe, spore forming

Source/exposure to chlostridium spp.

C. perfringes (meat/poultry) and C. botulinum (canned goods)

Pathogenesis for C. perfringens in chlostridium spp.

More common, enterotoxin

Pathogenesis for C. botulinum in chlostridium spp.

More dangerous, botulin toxin.

Treatment for food posioning

Supportive treatment in extreme cases (e.g. fluids, electrolyte replacement)

Prevention of food poisoning

Sanitation in food production, preparation and storage

Pathogen for salmonella spp. (salmonellosis)

Gram-negative, facultative aerobe

Sources/exposure to salmonella spp. (salmonellosis)

Contaminated food, water, and animal contact (also chronic carriers).

Pathogenesis of salmonella spp. (salmonellosis)

Diverse virulence factors

Pathogen of camplyobacter spp.

Most common cause food infection, Gram-negative, microaerophile

Sources/exposure to camplyobacter spp.

Resident in poultry intestines (90%), antibiotics for severe cases.

Pathogenesis of camplyobacter spp.

Inflammation of intestinal epithelium

Pathogen for listeria monocytogenes (listeriosis)

Gram-positive, facultative aerobe; acid-, salt-, and cold-tolerant

Sources/exposure to listeria monocytogenes (listeriosis)

Unpasteurized dairy, prepackaged foods

Pathogenesis of listeria monocytogenes (listeriosis)

Infection cycle, in the severe cases it causes septicemia and meningitis

Animal-transmitted bacterial disease(s)

Psittacosis

Animal-transmitted viral diseases

Rabies, hantavirus

Rabies pathogen

Rhabdovirus

Rabies reservoirs

Domestic animals and wild animals

Rabies transmission

Infected animal bite

Rabies pathology

Virus in animal saliva, infects human host via animal bites, proliferates in the brain.

Symptoms of rabies

Excitation, anxiety, pupil dilation, excessive salivation (hydrophobia)

Diagnosis of rabies

Laboratory analysis, can only be tested once animal is dead (negri bodies).

Passive treatment for rabies

Anti-rabies virus antibodies

Active treatment for rabies

Rabies virus vaccine

Prevention of rabies

Immunization for humans and domestic animals; injection or oral vaccines for wild animals.

Hantavirus syndrome pathogen

Hantaviruses

Reservoir for hantavirus syndrome

Rodents (mice, rats, voles)

Transmission of hantavirus syndrome

Infected animal feces

Pathology of hantavirus syndrome

Inhalation of fecal dust from infected animals; proliferates in the human body

Symptoms of hantavirus pulmonary syndrome

Fever, muscle pain, thrombocytopenia (decrease in platelets), leukocytosis (increase in leukocytes)

Diagnosis for hantavirus pulmonary syndrome

Laboratory tests: virus cultures, ELISA, PCR

Treatment for hantavirus pulmonary syndrome

No treatment for vaccines available

Pathogen for psittacosis

Chlamydia psittaci

Reservoir for psittacosis

Birds (parrots, poultry)

Transmission of psittacosis

Infected animal feces, infected animal saliva

Pathology for psittacosis

Inhalation of fecal dust from pets or poultry; causes lung infection (pneumonia) in severe cases, death in rare cases.

Symptoms of psittacosis

Fever, headache, dry cough; similar to other respiratory infections

Diagnosis for psittacosis

Molecular tests (PCR)

Treatment for psittacosis

Antibiotics (e.g. tetracycline), no vaccines available.

Prevention of psittacosis

Awareness for safe bird and cage care.

Arthropod-transmitted bacterial diseases

Lyme disease and plague

Arthropod-transmitted viral diseases

West Nile

Arthropod-transmitted protist diseases

Malaria and trypanosomiasis

Pathogen for lyme disease

Borrelia borgdorferi (bacteria)

Reservoir for lyme disease

Mammals (rodents)

Vector of lyme disease

Lxodes scapularis (ticks)

Pathology of lyme disease

If untreated, the disease can reach the CNS; no toxins or virulence factors known

Symptoms of acute stage lyme disease

Rash, headache, backache, chills, fatigue

Symptoms of chronic stage lyme disease

Arthritis (40-60%), neurological (15%), and heart damage (8%).

Diagnosis of lyme disease

Symptoms + tick exposure + rash

ELISA, Western blot, PCR assays

Treatment of lyme disease

Antibiotics amd vaccines (animals and humans).

Prevention of lyme disease

Reduce exposure to ticks, insect repellants, proper clothing, remove attached ticks.

Pathogen for the plague

Yersinia pestis (bacterium)

Reservoir for the plague

Rodents

Vector for the plague

Fleas

Pathology for the plague

Lymph node swelling (buboes) and infection in the bloodstream (septicemia)

Slyvatic

Flea vector for plague (affects rodents)

Bubonic

Flea vector for plague (affects humans)

Pneumonic

Direct inhalation of plague (affects humans)

Septicemic

No buboes, most deadly form of plague (affects humans)

Treatment of bubonic plague

Antibiotics (early stage)

Treatment for pneumonic plague

Rapid disease progression, can be treated with antibiotics

Treatment for septicemic plague

No symptoms, death occurs before diagnosis is possible.

Prevention of the plague

Control animal reservoirs, vectors, and human contact. Plague infected animals must be destroyed.

Malaria pathogen

Plasmodium spp. (protist)

Reservoir of malaria

Humans and mosquitoes

Vector of malaria

Anopheles spp. (mosqutioes)

Symptoms of malaria

Chills, fever, headaches, anemia, enlarged spleen

Diagnosis of malaria

Infected red blood cells; PCR tests can determine species

Treatment for malaria

Chloroquine and primaquine

What does chloroquine do?

Kills merozoties, goes inside red blood cells.

What does primaquine do?

Kills merozoties, sporozites, and gamaetes; outside of the blood cells.

Prevention of malaria

High risk areas receive chloroquine and disrupt pathogen life cycle (eliminate mosquitoes + habitat)