Appendix A Signs and Symptoms of Arthropod-Borne Diseases The following is an alphabetical listing of common signs and symptoms of arthropod-borne diseases. Unfortunately, few signs and symptoms are specific to anyone disease. Further differen- tiation by appropriate laboratory or radiologic tests may be needed. By no means should this listing be considered as a com- plete differential diagnosis of any of the symptoms discussed. Adenopathy: Generalized adenopathy may occur in the early stages of African trypanosomiasis-the glands of the poste- rior cervical triangle being most conspicuously affected (Winterbottom's sign). Adenopathy may also be seen in the acute stage of Chagas' disease. Anemia: Anemia may be seen in cases of malaria, babesiosis, and trypanosomiasis. Anemia can be especially severe in falciparum malaria. Blister: A blister may occur at arthropod bite sites. Blistering may also occur as a result from blister beetles contacting human skin. Bulls-Eye Rash (See Erythema Migrans) Chagoma: An indurated, erythematous lesion may occur on the body-often head or neck-caused by Trypanosoma cruzi infection (Chagas'disease). A chagoma may persist for 2-3 mo . Chyluria: The presence of chyle (lymphatic fluid) in the urine is often seen in lymphatic filariasis. Urine may be milky white and even contain microfilariae. Coma: Sudden coma in a person returning from a malarious area may indicate cerebral malaria. African trypanosomia- sis (sleeping sickness) may also lead to coma after a long period of increasingly severe symptoms of meningoencepha- litis. Rocky Mountain Spotted Fever and other rickettsial infections may also lead to coma. 203
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Appendix A
Signs and Symptoms of Arthropod-Borne Diseases
The following is an alphabetical listing of common signs and symptoms of arthropod-borne diseases. Unfortunately, few signs and symptoms are specific to anyone disease. Further differentiation by appropriate laboratory or radiologic tests may be needed. By no means should this listing be considered as a complete differential diagnosis of any of the symptoms discussed.
Adenopathy: Generalized adenopathy may occur in the early stages of African trypanosomiasis-the glands of the posterior cervical triangle being most conspicuously affected (Winterbottom's sign). Adenopathy may also be seen in the acute stage of Chagas' disease.
Anemia: Anemia may be seen in cases of malaria, babesiosis, and trypanosomiasis. Anemia can be especially severe in falciparum malaria.
Blister: A blister may occur at arthropod bite sites. Blistering may also occur as a result from blister beetles contacting human skin.
Bulls-Eye Rash (See Erythema Migrans) Chagoma: An indurated, erythematous lesion may occur on
the body-often head or neck-caused by Trypanosoma cruzi infection (Chagas'disease). A chagoma may persist for 2-3 mo.
Chyluria: The presence of chyle (lymphatic fluid) in the urine is often seen in lymphatic filariasis . Urine may be milky white and even contain microfilariae.
Coma: Sudden coma in a person returning from a malarious area may indicate cerebral malaria. African trypanosomiasis (sleeping sickness) may also lead to coma after a long period of increasingly severe symptoms of meningoencephalitis. Rocky Mountain Spotted Fever and other rickettsial infections may also lead to coma.
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Conjunctivitis: Chagas' disease and onchocerciasis may lead to chronic conjunctivitis.
Dermatitis: Several arthropods may directly or indirectly cause dermatitis. Chiggers and other mites may attack the skin, causing a maculopapular rash. Scabies mites may burrow under the skin's surface making itchy trails or papules. Lice may give rise to hypersensitivity reactions with itchy papules. Chigoe fleas burrow in the skin (especially on the feet), causing local irritation and itching. Macules or erythematous nodules may result as a secondary cutaneous manifestation of leishmaniasis.
Diarrhea: Leishmaniasis (and specifically visceral leishmaniasis-kala-azar) may lead to mucosal ulceration and diarrhea. In falciparum malaria, plugging of mucosal capillaries with parasitized red blood cells may lead to watery diarrhea.
Edema: Edema may result from arthropod bites or stings. Loiasis (a nematode worm transmitted by deer flies) may also cause edema-a unilateral circumorbital edema as the adult worm passes across the eyeball or lid. Passage of the worm is brief, but inflammatory changes in the eye may last for days. Loiasis may also lead to temporary appearance of large swellings on the limbs, known as Calabar swellings at the sites where migrating adult worms occur. Unilateral edema of the eyelid, called Romana's sign, may occur in Chagas' disease. African trypanosomiasis (sleeping sickness) may result in edema of the hips, legs, hands and face.
Elephantiasis: Hypertrophy and thickening of tissues, leading to an "elephant leg" appearance, may result from lymphatic filariasis. Various tissues may be affected, including limbs, the scrotum, and the vulva.
Eosinophilia: Helminth worms may cause eosinophilia. Atopic diseases, such as rhinitis, asthma, and hay fever also are characterized by eosinophilia.
Eosinophilic Cerebrospinal Fluid Pleocytosis: Cerebrospinal fluid eosinophilic pleocytosis can be caused by a number of infectious diseases (including rickettsial and viral infections), but is primarily associated with parasitic infections.
Epididymitis: Epididymitis, with orchitis, may be an early complication of lymphatic filariaisis.
Erythema Migrans: Erythema migrans may follow bites of ticks infected with the causative agent of Lyme disease, Bor-
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relia burgdorferi. Typically the lesion consists of an annular erythema with a central clearing surrounded by a red migrating border. Although erythema migrans does not always occur, it is virtually pathognomonic for Lyme disease.
Eschar: A round (generally 5-15 mm) spot of necrosis may result from boutonneuse fever (a spotted fever group illness) or scrub typhus. An eschar develops at the site of tick or chigger bite.
Excoriation: Lesions produced by "self-scratching" may be a sign of imaginary insect or mite infestations (delusions of parasitosis).
Fever: Fever is a common sign of many arthropod-borne diseases, including the rickettsioses, thyphus, dengue, yellow fever, plague, the encephalitides, and others. In some cases, there are cyclical peaks of fever, such as in relapsing fever (tick-borne) or malaria. Falciparum malaria is notorious for causing extremely high fever (107°F or higher). Filariasis may be marked by fever, especially early in the course of infection.
Hematemesis: Coffee-ground color or black vomit may be a sign of yellow fever .
Hemoglobinuria: Falciparum malaria can cause "blackwater fever."
Hydrocele: Hydrocele may result from lymphatic filariasis, developing as a sequel to repeated attacks of orchitis.
Kerititis: Inflammation of the cornea is sometimes a result of ocular migration of Onchocerca volvulus microfilariae. It may lead to blindness.
Leukopenia: Leukopenia is a prominent finding in cases of ehrlichiosis. It may also occur (3000-6000/ mm3) with a relative monocytosis during the afebrile periods of malaria.
Lymphadenitis: Inflammation of one or more lymph nodes may be a sign of lymphatic filariasis-especially involving the femoral, inguinal, axillary, or epitrochlear nodes.
Lymphangitis: Lymphangitis can be an early symptom of lymphatic filariasis, involving the limbs, breast, or scrotum.
Lymphocytosis: Lymphocytosis may occur in Chagas' disease. Maggots: The presence of fly larvae in human tissues is termed
myiasis. Various blow flies, bot flies, and other muscoid flies are usually involved.
Meningoencephalitis: Meningoencephalitis has many causes, but may be a result of trypanosomes in the case of African
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trypanosomiasis (sleeping sickness) or Chagas' disease (although generally milder). Falciparum malaria infection may be cerebral, with increasing headache and drowsiness over several days, or even sudden onset of coma.
Myocarditis: Chagas' disease may lead to myocardial infection. African trypanosomiasis may also cause myocarditis to a lesser extent.
Neuritis: Neuritis may be caused by bee, ant, or wasp venom. Occasionally stings to an extremity result in weakness, numbness, tingling, and prickling sensations for days or weeks. Neuritis may also result from infection with the Lyme disease spirochete.
Nodules, Subcutaneous: Onchocerciasis may present as skin nodules (see Onchocercoma). Tick bites may also result in nodules. Fly larvae in the skin (myiasis) may also present as nodules. Common species involved are the human botfly larva, Dermatobia hominis, the Tumbu fly, Cordylobia anthropophaga, and rodent botfly larvae, Cuterebra spp.
Onchocercoma: Coiled masses of adult O. volvulus worms beneath the skin enclosed by fibrous tissues may occur in patients living in tropical countries endemic for ochocerciasis.
Orchitis: Orchitis may be a symptom of lymphatic filariasis; repeated attacks may lead to hydrocele.
Paralysis: Ascending flaccid paralysis may result from tick attachment. The paralysis is believed to be caused by a salivary toxin injected as the tick feeds.
Proteinuria: Proteinuria, with hyaline and granular casts in the urine, often occurs in falciparum malaria.
Puncta: A small, point-like pierce mark may mark the bite or sting site of an arthropod. Paired puncta may indicate spider bite or centipede bite.
Rash: There are myriad causes of rash, but rash may accompany many arthropod-borne diseases, such as Rocky Mountain Spotted Fever, ehrlichiosis, murine typhus, and African trypanosomiasis. The rash may appear to be ring-like, and expanding in the case of Lyme disease (see Erythema Migrans). An allergic urticarial rash may be seen in the case of bites or stings.
Romana's Sign: A common sign early in the course of Chagas' disease, Romafia's sign is a unilateral palpebral edema, involving both the upper and lower eyelids. This generally
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occurs when a kissing bug (the vector of the Chagas' organsism) bites near the eye.
Shock: Shock may occur from arthropod stings (rarely bites) as a result of hypersensitivity reactions to venom or saliva. Shock may also accompany falciparum malaria.
Splenomegaly: Splenomegaly can be a result of lymphoid hyperplasia in both African and American trypanosomiasis. It may also occur in visceral leishmaniasis (kala-azar).
Tachycardia: Both African and American trypanosomiasis may produce tachycardia. In Chagas' disease tachycardia may persist into the chronic stage where it may be associated with heart block.
Ulcers, Cutaneous: A shallow ulcer (slow to heal) may be a sign of cutaneous leishmaniasis. In the New World,lesions from cutaneous leishmaniasis are most often found on the ear. Also, a firm, tender, raised lesion up to 2 cm or more in diameter may occur at the site of infection in African trypanosomiasis.
Urticaria: Urticaria may result from an allergic or generalized systemic reaction to arthropod venom or (more rarely) saliva.
Verruga Peruana: A benign dermal eruption (peruvian warts) is one manifestation of bartonellosis. The verrugae are chronic, lasting from several months to years, and contain large numbers of Bartonella bacilliformis bacteria.
Winterbottom's Sign: In the early stages of African trypanosomiasis, patients may exhibit posterior cervical lymphadenitis.
Appendix B
Diagnostic Tests Used in Arthropod-Borne Diseases
1. Agglutination
Agglutinations are antibodies that cause clumping together (agglutination) of microorganisms, erythrocytes, and often antigenic particulates. If the serum being tested is specific, agglutinins present will cause cultured parasites or bacteria to clump when the serum is introduced.
2. Complement Fixation
In CF tests, the suspected serum is incubated with a known source of antigen, permitting the antigen-antibody interaction to bind complement and remove it from the reaction mixture. A sheep-blood indicator is then added which hemolyzes in the presence of free complement. If the sheep cells fail to hemolyze, complement is absent; its absence testifies to the prior occurrence of an antigen-antibody reaction. By varying the serum or antigen dilution, one can achieve a crude approximation of titer.
3. Direct Fluorescent Antibody
A DFA test (some texts refer to it as direct immunofluorescence or DIF) utilizes fluorescent tagging of antibodies produced against the pathogen in question. These tagged antibodies can be purchased commercially against a wide variety of organisms. When tagged antibodies are placed on a microscope slide containing the pathogen, the organisms fluoresce when viewed by fluorescent microscopy. DFA is a one-step procedure involving the placement of tagged antibody on a suspect smear of tissue or blood and viewing (after a brief phosphate-buffered saline [PBS] wash) with a UV light-equipped microscope.
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4. Enzyme Immunoassay (EIA)
There are numerous modifications, but in general, EIA determines the presence or absence of an organism by the reaction between the suspected organism's antigen or antibodies, an enzymecoupled corresponding antibody or antigen, and an enzyme substrate. Color is generated by the interaction of a chromogenic substrate and an enzyme that has been coupled to the detector antibody. Degree of color change is dependent on the concentration of antibody or antigen present, and can be assayed either qualitatively or quantitatively.
5. Enzyme-Linked Immunosorbent Assay (ELISA)
Similar in principal to EIA, the ELISA test may be used for quantitative determination of either antigen or antibody. The appropriate antigen or antibody is bound to (usually) plastic micro titer plates, and the specimen to be tested is then added and given time to react with the already present antigen or antibody. After a wash to remove any unbound test material, an enzyme-linked antigen or antibody is added. After a second wash, a substrate is added that will react with the remaining enzyme to produce a color change.
6. Hemagglutination Inhibition (HI)
The HI test measures the presence of hemagglutination-inhibiting antibody toward a particular organism. The suspected serum is incubated with fluid medium known to be capable of agglutinating red cells. After the incubation period, the agglutinating potency is measured, and the absence of subsequent agglutination indicates the presence of specific antibodies in the serum.
7. Indirect Fluorescent Antibody (IFA)
The IFA test is a two-step test involving the placement of patient serum suspected of containing antibodies on a slide with fixed, known antigen. After an incubation period and PBS washing, the slide is then covered with a solution containing fluorescent-tagged antihuman antibodies. After a second incubation period and PBS washing, the slide is viewed by fluorescent microscopy. Fluorescence of antigen on the slide is considered evidence of patient
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antibodies toward that particular organism. By serially diluting patient serum, a titer can be determined.
8. Leishmanin (Montenegro Test)
The leishmanin test (not available in the United States) is sometimes used to help diagnose cases of cutaneous and muco-cutaneous leishmaniasis. It involves an intradermal injection of a suspension of killed promastigotes. A high percentage of Leishmania tropica and Leishmania braziliensis infections will test positive by this test.
9. Mazzotti
The Mazzotti test is used to determine if a patient has onchocerciasis. It can be dangerous and is not used in many areas. It consists of oral administration of 25 or 50 mg of diethylcarbamazine to a patient suspected of having onchocerciasis. If the patient is infected, an intense itching occurs in a few hours (as the microfilariae die within the skin). The itching is then controlled by shortterm administration of corticosteroids, or will subside on its own within 2-3 d.
10. Neutralization
The neutralization test (NT) is the most specific immunologic test for the majority of viral infections. The identification of an unknown viral isolate is made by analyzing the degree to which antisera of known reactivity prevent the virus from infecting tissue-culture cells, eggs, or animals. If neutralizing antibody is present, virus cannot attach to cells, and infectivity is blocked
11. Polymerase Chain Reaction (PCR)
The peR has dramatically changed diagnostic microbiology in recent years. peR makes specific identification of pathogens possible, even when only a few organisms are present. peR is a highly sensitive technique by which minute quantities of DNA or RNA sequences are enzymatically amplified to the extent that a sufficient quantity of material is available to reach a threshold signal for detection using a specific probe. The scientific basis of peR is that each infectious disease agent (in fact, every living
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thing) possesses a unique signature sequence in its DNA or RNA by which it can be identified. In other words, there is a unique sequence of amino acids for each organism. By finding those unique sequences and constructing primers to amplify those specific areas of DNA, identification of an organism can be accomplished from a blood or tissue sample, or even from an infected arthropod vector. peR is carried out using a thermocycler, which produces a series of heat-cool cycles, whereby double-stranded DNA is dissociated into single strands that are in turn allowed to anneal in the presence of specific primers on cooling. Through the successive heat-cool cycles (usually about 30), the DNA sequence to be detected is amplified millions of times. The product is then visualized after separation on agarose gels by electrophoresis and appropriate staining.