Chapter 96. Foodborne and Waterborne Diseases

Foodborne disease is an illness that occurs in 2 or more people after the consumption of common food source. Contamination can come from bacteria, viruses, or protozoans. Viruses are the most common source, including Norwalk-type (58% overall, United States), astrovirus, rotaviruses, and enteric adenoviruses. Bacterial sources include nontyphoidal Salmonella (11% overall, most common cause for hospitalization and associated death in the United States), Clostridium perfringens, Campylobacter spp, Listeriamonocytogenes, Shigella spp, Shiga toxin producing Escherichia coli (STEC) and Staphylococcus aureus. Parasitic causes include Giardia lamblia, Toxoplasma gondii, Entamoeba histolytica, and Cryptosporidium. The most common associated foods are poultry, leafy vegetables, and fruits/nuts. In addition, after eating reef fish that feed on certain dinoflagellates (algae), patients may experience scombroid or ciguatera poisoning which is a toxin induced syndrome.

Waterborne diseases occur from ingestion of, or contact with contaminated water, from swimming pools, hot tubs, spas, or naturally occurring fresh or salt water. Symptoms are can be either GI or dermatologic. Common organisms include the majority of those associated with foodborne illness plus Vibrio species, Aeromonas species, Pseudomonas aeruginosa, Yersinia species, Hepatitis A, nontuberculous Mycobacterium and less frequent organisms.

Symptoms of both foodborne and waterborne illness include vomiting, diarrhea, abdominal cramping, fever, dehydration, malaise, and in some, bloody stool. Physical exam may be remarkable for features of dehydration, and in some, stool positive for frank or occult blood. Prolonged illness beyond 2 weeks suggests protozoan parasites. STEC may be complicated by hemolytic uremic syndrome (decreased urine output, symptoms of anemia), especially after antibiotic treatment. STEC classically presents with vomiting, moderate to marked stomach cramps, diarrhea (often bloody) and mild fever, not over 101°F/38.5°C.

Patients with scombroid fish poisoning or ciguatera poisoning have symptoms similar to foodborne illness described immediately above, 1 to 24 hours after ingestion of reef fish. In addition, patients with scombroid poisoning frequently have flushing and headache due to histamine reaction. Those with ciguatera poisoning may have headaches, muscle aches, paresthesias, or a burning sensation on contact with cold, due to sodium channel mediated nerve depolarizations. Neurologic symptoms may be prolonged beyond the ED visit.

The skin manifestations of waterborne illness vary from simple cellulitis, the painful indurated plaque of Mycobacterium marinum, to necrotizing infections which may include hemorrhagic bulla with Vibrio vulnificus. Patients with Aeromonas hydrophila skin infections often have a history of trauma associated with freshwater exposure, and may have foul smelling wounds.

Bedside testing for fecal occult blood is the most commonly indicated test; otherwise most patients need no laboratory testing, unless significantly dehydrated or other significant diagnoses are being considered. For those more acutely ill, consider fecal leukocytes, the neurophil marker lactoferrin, electrolytes, and complete blood count. Stool gram stain may reveal Campylobacter. Stool cultures are more likely to be positive in those with positive fecal leukocytes or lactoferrin. STEC and Vibrio cultures require specific procedures (check local laboratory guidelines). Reserve ova and parasite testing for those patients with chronic symptoms, immunocompromise, or patients with a confirmed source of parasite. Other considerations include Rotavirus antigen testing in children from daycare settings, daycare workers, or older adults. Clostridium difficile antigen testing may be indicated in those with prolonged symptoms, recent antibiotic use, significant comorbidities, or extremes of age.

Most cases are self-limited and improve with nonspecific treatment.

1. Initiate oral rehydration fluids initially if tolerated. Intravenous rehydration with normal saline will benefit those significantly dehydrated, or those with continued vomiting.

2. Antiemetics, such as metoclopramide 10 milligrams PO or IV, or ondansetron 4 milligrams PO or IV may facilitate oral rehydration. Antihistamines, such as diphenhydramine 25 milligrams PO or IV, may improve the symptoms of scombroid fish poisoning.

3. Loperamide 4 milligrams initially, then 2 milligrams after every unformed stool up to a maximum of 16 milligrams/d is indicated in mild to moderate, nonbloody diarrhea in adults without fever (do not use in patients with STEC).

4. Antibiotics are favored only in those patients with an increasing number of the following features: significant abdominal pain, bloody diarrhea, fever over 101°F/38.5°C, symptom duration > 48 hours, impaired host, positive fecal leukocytes or lactoferrin, however, antibiotics are contraindicated in patients with STEC. When treatment is indicated, recommended agents include ciprofloxacin 500 milligrams PO twice per day, or trimethoprim-sulfamethoxazole double-strength twice daily, for 3 to 5 days. Organism specific antibiotic recommendations can be found in the parent text sited at the end of this chapter.

5. Vibrio vulnificus skin infections are treated with doxycycline 100 milligrams IV or PO twice daily, plus ceftazidime 2 grams IV every 8 hours. Aeromonas skin infections are treated with ciprofloxacin 500 milligrams twice daily (mild cases) or with piperacillin-tazobactam 3.375 grams IV every 6 hours in severe cases. Necrotizing infections require emergent surgical debridement.

6. Most patients can be treated as outpatients, admission is indicated in those appearing toxic, those in whom vomiting cannot be controlled, the immunocompromised, or those at the extremes of age with significant symptoms.