What diseases can fleas carry?

Diseases Transmitted by Fleas

Fleas are vectors for several serious diseases, most notably plague (Yersinia pestis), murine typhus (Rickettsia typhi), and bartonellosis, with plague representing the highest mortality risk if untreated.

Major Flea-Borne Diseases

Plague (Yersinia pestis)

• Plague is the most critical flea-borne disease, transmitted primarily through bites from infected fleas, particularly Xenopsylla cheopis (rat fleas), with an untreated case-fatality rate of 50-60% for bubonic plague 1.
• The disease presents in three forms: bubonic (80-90% of cases), septicemic, and pneumonic, with pneumonic plague being universally fatal without treatment within 18 hours of respiratory symptom onset 1.
• More than 80 flea species worldwide can transmit plague, including Xenopsylla cheopis, X. brasiliensis, Synopsyllus species, Pulex irritans, and Paractenopsyllus pauliani 2.
• Transmission occurs when fleas feed on infected rodents and subsequently bite humans, with 78% of U.S. plague cases attributed to flea bites 1.

Rickettsial Diseases

• Murine typhus (caused by Rickettsia typhi) is transmitted by fleas, particularly Xenopsylla cheopis and Ctenocephalides species from cats and dogs 3.
• Rickettsia felis and R. conorii have been identified in fleas and can cause spotted fever-like illnesses 4, 3.
• Molecular evidence confirms the presence of these rickettsial pathogens in cat and dog fleas in multiple countries including India 3.

Bartonellosis

• Cat-scratch disease (caused by Bartonella henselae) is transmitted by cat fleas (Ctenocephalides felis) 1, 4.
• Bartonella species can cause trench fever and other systemic infections in humans 5.
• Up to 80% of fleas collected from cats contain at least one organism capable of causing illness in cats or humans 4.

Parasitic Infections

• Tapeworm infection (Dipylidium caninum) occurs when children accidentally swallow infected fleas 1.
• This is particularly concerning in settings where children have close contact with animals harboring fleas 1.

Clinical Significance and Mortality Risk

High-Risk Scenarios

• Pneumonic plague requires treatment within 18 hours of respiratory symptom onset to prevent death 1.
• Septicemic plague carries a 50% mortality rate even with historical treatment approaches 1.
• Bubonic plague, if untreated, has a 50-60% case-fatality rate 1.

Geographic Distribution

• Plague remains endemic in regions of Asia, Africa, the Americas, and southeastern Europe near the Caspian Sea 1.
• In the United States, 80% of plague cases occur in southwestern states (New Mexico, Arizona, Colorado) 1.
• Plague outbreaks have been documented in Madagascar, India, and other developing nations 2, 3.

Prevention Priorities

Vector Control

• Flea control is essential for preventing disease transmission, particularly in areas with rodent populations near human habitation 1.
• Combination of insecticidal products and insect growth regulators provides the most effective flea control 5.
• Use of flea and tick control products on pets blocks transmission of multiple pathogens 4.

High-Risk Exposures to Avoid

• Direct contact with sick or dead rodents and their fleas poses the greatest plague risk 1.
• Handling infected domestic cats can transmit plague through scratches, bites, or respiratory droplets 1.
• Occupational exposures in veterinary settings or with exotic animals increase risk for multiple flea-borne diseases 1.

Critical Pitfall

• Do not delay antibiotic treatment when plague is suspected—streptomycin or doxycycline should be initiated immediately based on clinical suspicion, as waiting for laboratory confirmation can be fatal 1.