ZOONOTIC INFECTIONS (ARTHROPODS): DISEASE PROCESS ANALYSISa. Definition: diseases and infections that are naturally transmitted between

vertebrate animals and humans. broad class of diseases includes >200 specific diseases and

syndromes covering an extremely variable range of clinical syndromes and medical therapy. (WHO)

b. Epidemiology: >4 million people (in North America) are estimated to be infected annually

represent a significant public health problem in underdeveloped regions dependent economically on agricultural animals.

c. Etiology: Zoonotic infections can be transmitted to humans by direct contact with an infected animal or infected animal product, by ingestion of contaminated water or food products, by inhalation, and through arthropod vectors.

more zoonotic diseases are transmitted by ticks than by any other vector.

d. Pathogenesis:

RISK FACTORSRisk Category Examples

Agricultural workers Farmers, cattle ranchers, sheep ranchers, and migrant workers

Animal processing workers Slaughterhouse workers, animal hide processors, and workers in any manufacturing plant that deals with animal products or by-products

Outdoor enthusiasts Forestry workers, lumbermen, surveyors, park rangers, hunters, spelunkers, fishermen, and those who regularly engage in outdoor recreational activities

Pet owners Those with a dog, cat, bird, rodent, rabbit, reptile, or fish

Professionals Veterinarians, animal researchers, and animal handlers

Immunocompromised patients Those with congenital immunodeficiencies, diabetes mellitus, alcoholism, renal failure, liver failure, cancer, splenectomy, or human

immunodeficiency virus

Patient History questions: Tick exposure (risk of zoonotic illness transmission, particularly of

rickettsial disease)o Many patients do not recall a history of a tick bite.

type of animal exposure dressing, skinning, or handling an animal’s skin history of animal bite or scratch ingestion of animal or dairy products Bush meat hunting (particularly high-risk exposure activity) Recent travel, particularly in spring, summer, and early fall months in the U.S., most zoonoses show an increased incidence in the spring

and summer history of habitation particularly in an underdeveloped country or

rural area

e. Gross appearanceCommon Systemic Zoonotic Infections (related to case only)

Agent Animal Reservoir Physical Findings Diagnostic

Tests Treatment

Chlamydophila psittaci (formerly Chlamydia psittaci)

Birds Fever, flulike illness, pneumonia, endocarditis, sepsis

Serologic testing and sputum culture

Doxycycline or erythromycin

Coxiella burnetii (Q fever)

Cats, livestock animals, ticks

Fever, pneumonia, hepatitis, meningitis, endocarditis

Serologic testing

Doxycycline, with the possible addition of a fluoroquinolone or hydroxychloroquine

Ehrlichia species

Ticks Nonspecific fever, sepsis, meningitis, hepatitis

Serologic testing, peripheral blood smear, immunocytologic testing, polymerase chain reaction testing

Doxycycline, rifampin in pregnant woman

Francisella species (tularemia)

Rabbits, cats, wild animals

Fever, sepsis, meningitis, pneumonia, hepatitis, rash

Serologic testing

Piperacillin-tazobactam, third-generation cephalosporin, aminoglycoside, fluoroquinolone, or tetracycline

Rickettsia rickettsii

Ticks Fever, diarrhea, or typical presentation of Rocky

Rise in antibody titer

Doxycycline or chloramphenicol

Mountain spotted fever between acute and convalescent serum, skin biopsy

Yersinia pestis Dogs, cats, rodents

Bubonic: fever, headache, buboes, or pneumonic: cough, chills, dyspnea, shock

Blood culture, culture of suspected sites

Doxycycline, fluoroquinolone, gentamicin, streptomycin, or chloramphenicol

Tickborne Zoonotic InfectionsDisease Vector Animal

Reservoir Clinical Features Geographic Distribution

Babesiosis Ixodes dammini, I. scapularis, and I. pacificus

Cattle, horses, dogs, cats, rodents, deer

Fatigue, malaise, anorexia, nausea, headache, sweats, rigors, abdominal pain, emotional lability, depression, dark urine, hepatomegaly, fever, petechiae, ecchymosis, occasional rash, and, occasionally, pulmonary edema

Coastal areas of ME, MA, RI, and NY; also in MD, CT, VA, MN, WI, GA, WA, and Mexico

Colorado tick fever

Dermacentor andersoni

Deer, marmots, porcupines

Fever, chills, headache, myalgias, nausea, vomiting, photophobia, abdominal pain, and occasional sore throat; also may have conjunctivitis, lymphadenopathy, hepatosplenomegaly, stiff neck, retro-orbital pain, weakness, and lethargy

Western and northwestern U.S. and southwestern Canada

Anaplasmosis I. scapularis Dogs, deer, other mammals

Fevers, chills, malaise, headache, nausea, muscle aches, cough, sore throat, and pulmonary infiltrates (especially in children)

Japan, Malaysia, and the eastern, northeastern, and north-central U.S.

Ehrlichiosis (human monocytic ehrlichiosis)

Amblyomma americanum (lone star tick) and D. variabilis

Dogs, deer, other mammals

Fevers, chills, malaise, headache, nausea, muscle aches, cough, sore throat, and pulmonary infiltrates (especially in children)

Japan, Malaysia, and southeastern U.S.

Lyme disease (Borrelia burgdorferi)

I. dammini Deer, sheep, deer mice

Erythema migrans, meningitis, encephalitis, neuropathy, and joint and heart symptoms

Atlantic central and north-central U.S.

Rocky Mountain spotted fever (Rickettsia rickettsii

D. andersoni (wood tick) and D. variabilis (dog tick)

North American mammals

Petechiae, purpura, pulmonary infiltrates, jaundice, myocarditis, hepatosplenomegaly, meningitis, encephalitis, and lymphadenopathy

Most of the continental U.S., although more prevalent in the southeast and south-central U.S.

Relapsing fever (Borrelia species)

Ornithodoros species

Human body lice, wild rodents, humans

Fever, chills, headache, myalgias, and arthralgias; pain, nausea, vomiting, and hypotension

Worldwide

Tularemia (Francisella tularensis)

Dermacentor species and Amblyomma species

Rabbits, deer, dogs

Pneumonia, regional lymphadenopathy and headache, cough, myalgias, arthralgias, nausea, vomiting, ulceration at inoculation site, and ocular findings

U.S. (except Hawaii) and Canada

Abbreviations: CT = Connecticut; GA = Georgia; MA = Massachusetts; ME = Maine; MN = Minnesota; NY = New York; RI = Rhode Island; VA = Virginia; WI = Wisconsin; WA = Washington; MD = Maryland.

f. Clinical Manifestations:

g. Pathophysiology of pain:

h. Natural History and Prognosis:

i. DiagnosisZoonotic infections should be considered part of the differential diagnosis of any undifferentiated infectious syndrome: fever, headache, myalgias, malaise, and weakness.

Tickborne diseases should be considered in the differential diagnosis of nonspecific febrile illnesses, especially if there is an associated rash.

However, diagnosis is difficult.

j. Treatment

Zoonoses and Arthropod-borne diseases

• rocky mountain spotted fever a. General characteristics

Caused by the intracellular bacteria Rickettsia rickettsii

Ticks feeding on various mammals serve as vectors for disease transmission.

The major endemic areas include the southeastern, midwestern, and west- ern United States. Peak incidence is in the spring and summer months due to increased outdoor activity.

Pathophysiology of disease

Organisms enter the host cells via tick bites, multiply in the vascular endothe- lium, and spread to different layers of the vasculature.

Damage to the vascular endothelium results in increased vascular permeability, activation of complement, microhemorrhages, and microinfarcts.

• B. clinical features

The onset of symptoms is typically 1 week after the tick bite.

It classically presents with a sudden onset of fever, chills, malaise, nausea, vomit-

ing, myalgias, photophobia, and headache.

• Papular rash usually appears after 4 to 5 days of fever. Rash starts peripherally (wrists, forearms, palms, ankles, and soles) but then spreads centrally (to the rest of the limbs, trunk, and face). It becomes maculopapular, and eventually petechial.

• It may lead to interstitial pneumonitis.

c. diagnosis

a. Diagnosis is primarily clinical. Laboratory abnormalities may include elevated liver enzymes and thrombocytopenia.

b.Acute and convalescent serology and immunofluorescent staining of skin biopsy are confirmatory tests.

d. treatment

1.Doxycycline—usually given for 7 days; given intravenously (IV) if the patient is vomiting

2.CNS manifestations or pregnant patients—give chloramphenicol

malariaa. General characteristics

1.A protozoal infection caused by one of four organisms a. Plasmodium falciparumb. Plasmodium ovalec. Plasmodium vivax d. Plasmodium malariae

2.Prevalent in tropical climates, parts of Africa and the Middle East

3.Transmitted via mosquito bite in endemic areas

B. clinical features

• Symptoms may include fever and chills, myalgias, headache, nausea, vomiting, and diarrhea.

• Fever pattern varies depending on causea. P. falciparum—fever is usually constantb. P. ovale and P. vivax—fever usually spikes every 48 hours c. P. malariae—fever usually spikes every 72 hours

c. diagnosis

1. Identify organism on peripheral blood smear 2. Blood smear must have Giemsa stain

d. treatment

c. Use chloroquine phosphate unless resistance is suspected. In many countries, chloroquine resistance is so prevalent that it should be assumed.

d.If chloroquine resistance is suspected, give quinine sulfate and tetracycline. Alternative agents are atovaquone-proguanil and mefloquine.

e. P. falciparum infection may require IV quinidine and doxycycline.

f. Relapses can occur in P. vivax and P. ovale infection as a result of dormant hypnozo- ites in the liver. Add a 2-week regimen of primaquine phosphate for these types of malarial infection.

g.Prophylaxis is important for travelers to endemic regions. Mefloquine is the agent of choice in chloroquine-resistant areas. Chloroquine can be used in areas where chloroquine resistance has not been reported.

References

Books:Step up to medicine 3rd edition, 2013, by Agabegi and AgabegiChapter 6, Connective tissue and joint disorders

Oxford handbook of clinical medicine, 7th edition, 2007 by Longmore, Wilkinson, Turmezei, Cheung, p. 873

Felson D.T. (2012). Chapter 332. Osteoarthritis. In Longo D.L., Fauci A.S., Kasper D.L., Hauser S.L., Jameson J, Loscalzo J (Eds), Harrison's Principles of Internal Medicine, 18e.