Infectious Disease

Selected Vector Borne Infections: Overview

These vector-borne diseases are spread from an infected host to a susceptible individual by way of the bite of a mosquito or tick.e They are not usually spread by direct contact with infected individuals; infections are infrequently transmitted through transfusion, organ transplant, shared needles, or sexual intercourse. Among cases of mosquito-borne infections diagnosed in the United States, chikungunya, dengue, Zika, and malaria are usually acquired through travel abroad. West Nile, and all of the rickettsial tick-borne infections have been reported to be acquired in the continental U.S., and the District of Columbia.28

The spectrum of illness severity is wide-ranging. Signs and symptoms may be fever, headache, myalgias, arthralgias, malaise and with or without a rash, from which the patient recovers completely, with an uneventful return to work. However, some cases involve complex multisystem involvement with serious manifestations such as neuroinvasive disease [encephalitis, meningitis, acute flaccid paralysis] that may require a prolonged convalescence before returning to work. Cognitive decline may interfere with the ability to perform essential job functions and should be assessed on an individual basis. This section is organized by agent type and vector: Fleas and mites are also vectors of relatively rare diseases, including plague, rickettsialpox, tularemia, murine typhus, and bartonellosis.

Viral Mosquito-borne

Chikungunya

General Description: An acute self-limited febrile illness with a 0.1% mortality rate. Predominant symptoms are fever and arthralgias, however the joint pain can persist for months. In one study, chronic arthralgia, fatigue, depression, and sleep disorders were twice as common in patients compared to seronegative controls. The most common neurological complications of chikungunya reported in a systematic review included: encephalitis, myelopathy, neuropathy, and optic neuritis.29

Mode of Transmission: Transmission is via Aedes mosquito vector. In the latest surveillance reports from CDC (2017), there were no locally acquired cases in the U.S., outside of Puerto Rico, and 114 cases were acquired abroad. Most imported cases were reported by California, New York, New Jersey, and Texas. However, locally acquired infections have been reported in past years in Florida.

Effect on LEO Fitness for Duty: Lower extremity arthralgias can last for years, and can be severely disabling resulting in a slow, broad-based halting gait. 30 In the Americas, one study cited 48% will develop a post-chikungunya “chronic inflammatory rheumatism.” Functional status and ability to perform essential job functions should be assessed on a case-by-case basis.

LEO-Specific Clinical Studies/Reports: None.

Dengue

General Description: A hemorrhagic fever virus infection with a clinical spectrum ranging from an acute febrile illness, with a 1% mortality rate, to dengue hemorrhagic fever, with an average mortality rate of 2-5% (with prompt treatment), and up to 50% (without treatment). Neuroinvasive disease has been well-documented, including encephalitis, meningitis, stroke, cerebellar syndrome, transverse myelitis. Peripheral neuropathies, including Guillain-Barre Syndrome, and isolated nerve palsies have been reported.31

Mode of Transmission: Vector borne (Aedes aegypti mosquito). Most cases diagnosed in the U.S. were acquired abroad by travelers to endemic regions in the Caribbean. History of locally acquired infections in small out-breaks in Texas, Florida; isolated cases in several other states and U.S. territories and possessions in the Caribbean and Pacific. Transfusion-associated infection reported in endemic regions. Sexual transmission has not been reported.

Effect on LEO Fitness for Duty: Several years after recovery from the acute illness, the most common sequelae reported in multiple studies were muscle and joint pain (30%), lack of energy (23%), muscle weakness, and general malaise. In one study,32 neuropsychological studies were “normal” however the specific battery of tests administered were not specified. Functional status and ability to perform essential job functions should be assessed on a case-by-case basis.

LEO-Specific Clinical Studies/Reports: None.

West Nile Virus

General Description: An acute illness consisting of fever, headache, and myaglias. In 2017, 68% of the 2,097 cases reported from 47 states and DC to CDC had neuroinvasive diseases. Of the cases with neuroinvasive disease, 50% were reported as encephalitis, 37% as meningitis, 6% as acute flaccid paralysis, and 6% as other neurologic illness. Most cases reported occurred in men, in the summer months.28

Mode of Transmission: Bite of the Culex mosquito

Effect on LEO Fitness For Duty: Sequellae of neuroinvasive disease may cause cognitive impairment (situational awareness, executive functioning, judgement, vigilance) or place patient at increased risk of seizure.33 Permanent motor weakness of the extremities has been reported.34

LEO-Specific Clinical Studies/Reports: Several reports in the lay press of law enforcement officers having contracted West Nile, but the relationship to the work environment has not been confirmed.

Zika

General Description: A mild illness manifested by a generalized maculopapular rash, arthralgias, headache and conjunctivitis, rarely requiring hospitalization – 80% of those infected with Zika are asymptomatic. Transplacental transmission with congenital microencephaly and ophthalmological abnormalities have been reported.

Mode of Transmission: Vector borne by the bite of the Aedes mosquito.

Effect on LEO Fitness for Duty: Neurologic complications in adults have been reported, including Guillain-Barre syndrome, encephalitis, transverse myelitis. Recovery varies widely. Functional status and ability to perform essential job functions should be assessed on a case-by-case basis.

LEO-Specific Clinical Studies/Reports: None.

Parasitic Mosquito-Borne 

Babesiosis

General Description: A febrile illness with headache, fatigue, chills, sweats and myalgias; not usually associated with a rash, caused by the intraerythrocytic parasite, Babesia sp. (commonly microti), Severity of illness may be dependent upon degree of parasitemia, and can be accompanied by thrombocytopenia, hemolytic anemia; co-infection with Lyme, ehrlichiosis, and anaplasma. Asymptomatic infection occurs in half the cases; complication rate highest among the immunosuppressed.

Mode of Transmission:  Transmitted by the bite of the tick,  Ixodes scapularis

Effect on LEO Fitness For Duty: The illness usually last for several weeks to months, occasionally with prolonged recovery that can last more than a year.35 Recovery varies widely. Functional status and ability to perform essential job functions should be assessed on a case-by-case basis.

LEO-Specific Clinical Studies/Reports: None.

Malaria

General Description: A febrile illness, commonly accompanied by chills, sweats, headaches, nausea and vomiting, body aches and general malaise (uncomplicated malaria). The severity of the illness is related to the specific species of the intraerythocytic parasite genus Plasmodium, general health of the host, and parasitemia. Severe malaria may involve multiple organ involvement including the central nervous system (cerebral malaria), blood (hemolytic anemia, coagulopathy), pulmonary (ARDS), renal (acute kidney injury, hemaglobinuria), and acid-base abnormality (metabolic acidosis).

Mode of Transmission: Bite of the female Anopheles mosquito

Effect on LEO Fitness For Duty: Recovery is dependent upon disease severity, which Plasmodium species is infecting the patient, and the promptness of treatment. Recovery varies widely. Functional status and ability to perform essential job functions should be assessed on a case-by-case basis.

LEO-Specific Clinical Studies/Reports: None.

Rickettsial Tick-borne

Anaplasmosis

General Description:   A febrile illness, accompanied by chills, headache, malaise, and rarely a rash in <10% of cases.  Case series suggest that anaplasmosis is most often a mild, self-limited illness that resolves without antibiotics.  Spectrum of disease ranges from asymptomatic infection to fatal disease;  death rate correlated with age, comorbid conditions, and severity.  Case reports of 36% hospitalization rate; 3% with life threatening complications; 17% requiring intensive care unit.  Most studied had thrombocytopenia.  Case reports of complications including sepsis syndrome, ARDS, pancarditis, acute renal failure, coagulopathy, and opportunistic secondary infections.  Neurologic complications reported were brachial plexopathy, demyelinating polyneuropathy, and acute transient sensorineural hearing loss.36

Mode of Transmission: Bite of the tick Ixodes scapularis. One cluster of cases in adult males after butchering a large quantity of white tail deer carcasses during hunting season.

Effect on LEO Fitness for Duty: Long term prognosis is favorable, with most recovering fully within 2 months. Functional status and ability to perform essential job functions should be assessed on a case-by-case basis.

LEO-Specific Clinical Studies/Reports:  None

Ehrlichiosis

General Description: An acute febrile illness accompanied by headache, malaise, myalgia, nausea, diarrhea. Ehrlichia chaffeensis infection is associated with rash in 30% of adults. Ehrlichiosis is a more severe disease than anaplasmosis, with case reports of a more than 45% of cases requiring hospitalization. Severe disease and death more common in immunocompromised patients, but fatalities have been reported in immunocompetent patients who present with a sepsis syndrome, toxic shock syndrome, or resembling Rocky Mountain Spotted Fever. The most frequent neurologic manifestation is meningitis or meningoencephalitis. CNS involvement is identified in approximately 20% of cases and may be associated with seizures and coma. In adults, subjective neurocognitive deficits following meningoencephalitis have been reported.

Mode of Transmission: Bite of the tick, Ixodes scapularis

Effect on LEO Fitness for Duty: Dependent upon severity of illness and complications.  Functional status and ability to perform essential job functions should be assessed on a case-by-case basis.

LEO-Specific Clinical Studies/Reports:   None reported

Lyme Disease

General Description: An infection caused by a spirochete, Borrelia burgdorferi. Early Lyme disease presents most commonly with the rash, erythema migrans, which begins as a papule or macule at the site of a tick bite, and progresses into a characteristic expanding bull’s-eye rash, which alternatively may be confluent). Erythema migrans may be asymptomatic or can be accompanied by nonspecific symptoms including severe fatigue, headache, arthralgia, myalgia, lymphadenopathy and less often, fever.37 Neuroinvasive signs in disseminated Lyme disease include cranial nerve palsies (frequently CN VII) and meningitis, presenting as aseptic meningitis.  Lyme carditis, which occurs in 4-10% of cases, commonly is associated with AV conduction block.

An asymmetric oligoarthritis, most commonly of the knee, is the most common feature of late Lyme disease; it was the initial presentation of Lyme Disease when it was first identified in 1975. However, with early recognition and treatment, the arthritis is seen now in only 10% of the cases. Most cases of Lyme disease can be successfully treated with 2-4 weeks of antibiotics; some patients have persistent of pain, fatigue, or cognitive impairment, which may take several months to resolve symptoms (Post-Treatment Lyme Disease Syndrome).

In one study evaluating cognitive decline in PTLDS, 124 patients with confirmed PTLDS underwent standard neuropsychological testing. The majority (92%) of participants endorsed some level of cognitive difficulty, yet 50% of the sample showed no statistically or clinically significant cognitive decline, 26% of the sample evidenced significant cognitive decline on measures of memory and variably on measures of processing speed, and 24% of the sample were excluded from analyses due to suboptimal test engagement. The authors concluded that their findings were consistent with the literature showing that the most robust neurocognitive deficit associated with PTLDS is in verbal memory and with variable decline in processing speed. Compared to population normative comparison standards, PTLDS-related cognitive decline remains mild.38

Mode of Transmission:  Through the bite of the deer tick, Ixodes scapularis

Effect on LEO Fitness For Duty: Cognitive impairment and oligoarthritis commonly of the knee as reported above. Functional status and ability to perform essential job functions should be assessed on a case-by-case basis, particularly those who have met the criteria for PTLDS.

LEO-Specific Clinical Studies/Reports: None.

Rocky Mountain Spotted Fever

General Description: An acute febrile illness, and a macular papular rash which does not appear in all cases. It is accompanied by headache, chills, malaise, myalgia, nausea, vomiting, abdominal pain, photophobia, and anorexia. Late complications include meningoencephalitis, acute renal failure, ARDS, cutaneous necrosis, shock, arrhythmia, and seizure.39  Focal neurologic deficits have been reported including motor nerve paralysis, transient hearing loss. Long term neurologic sequelae associated with severe disease, have been attributed to vasculopathy.

Mode of Transmission:  Bite of the dog tick, Dermacentor andersoni

Effect on LEO Fitness for Duty: Most cases respond to appropriate antibiotic treatment within a week. Persistent motor nerve deficits and cognitive impairment after timely treatment of the acute illness has been reported.40 Functional status and ability to perform essential job functions should be assessed on a case-by-case basis.

LEO-Specific Clinical Studies/Reports: None.

eFleas and mites are also vectors of relatively rare diseases, including plague, rickettsialpox, tularemia, murine typhus, and bartonellosis.