Case presentation

Case presentation Case 16 Reporter: I2 林士傑 Date: 94/11/28

Chief complaint, present illness, & personal/past/family history • A 17-year-old girl who had never traveled outside the United States, had recently spent the summer working as a waitress in Nantucket,Mass.On her return to her home in Washington, D.C., she developed a headache, fatigue, fever, shaking chills, joint and muscle aches, and other vague flu-like symptoms, which persisted for a month. • She had been previously healthy,al-though she had had a splenectomy due to injuries suffered in a ski accident.

Physical examination • headache,fatigue,fever,shaking chills joint and muscle aches, and other vague flu-like symptoms

Laboratory tests • Blood count, and thick and thin blood smears. The thin smears, stained with Giemsa stain, →intraerythrocytic,pleomorphic, ringlike and crucifix-shaped structures, found peripherally in the pale red blood cells.

Fig.16.1

Babesiosis (巴貝氏原蟲病) • Intraerythrocytic protozoan →malarialike illness

ETIOLOGY • Babesia, B. microti &B. divergens are the most that cause human infections. • Hosts→rodents,birds • Reservoir→Ticks • Vectors →Ixodid (hard-bodied) ticks Ixodes scapularis (I. dammini) I. ricinus,.

EPIDEMIOLOGY • Ticks is prevalent: Nantucket Island of Massachusetts Block Island in Rhode Island Long Island,Shelter Island, Fire Island in New York focal areas in Connecticut, Wisconsin, Minnesota • Between May~August • In Nantucket →60% of deer mice are infected with B. microti.

CLINICAL PRESENTATION • Varies widely and resembles malaria or rickettsiosis • Gradual onset of irregular fever, chills, sweating, muscle pain, and fatigue. • Mild hepatosplenomegaly and mild hemolytic anemia progressing to jaundice, hemoglobinemia, and renal failure. • The level of parasitemia may range from 1 to 50%.

DIAGNOSIS • History:tick bites, febrile persons living in endemic areas • Laboratory exam

Laboratory Findings • Hemolytic anemia, normal to low leukocyte counts, abnormal liver function. • Giemsa-stained blood smears :Ring forms & pleomorphic intraerythrocytic organisms on • Unlike malaria, Babesia organisms do not produce pigment in RBC • the absence of gametocytes and intracellular pigmentation help distinguish babesiosis from malaria. • Indirect immunofluorescenceantibody test

Giemsa-stain • For differentiate nuclear and/or cytoplasmic morphology of platelets, RBCs, WBCs, and parasites. • In Wright- and Giemsa-stain:  the cytoplasm appears blue.  the nucleus is relatively large, eccentrically located, and red.  the distinct, rod-shaped, red-staining kinetoplast (a specialized mitochondrial structure) contains extranuclear DNA arranged as catenated minicircles and maxicircles

TREATMENT • Intact spleen→self-limiting although symptoms may persist for months . • Clindamycin(1.2 g Bid IV or 600 mg Tid po for 7~10 days) Quinine(650mgTid po for 7 days) • Atovaquone(750mg po Bid for 7~10 days) Azithromycin(600 mg po Qd for 7~10 days) • Severe infections (parasitemia/asplenic)→in addition to exchange transfusions • Occasionally, pulmonary edema may develop after initiation of therapy.

Question 1 • What is the probable diagnosis of this patient's infection? Name the protozoanblood parasite which is most likely to be responsible for this infection.

Answer 1 • Dx→Babesiosis • Protozoan → B. microti & B. divergens are the two that cause most human infections

Question 2 • What are the ringlike and crucifix-shaped structures seen in the peripheralblood smear? Which aspect of the patient's history led to your conclusion abouther diagnosis? Do you think that her history of having a splenectomy would haveany relationship to her illness?

Answer 2 • Ringlike&crucifix-shaped structures→merozoite • Hints: 1.She had recently spent the summer working as a waitress in Nantucket,Mass. 2.She had had a splenectomy due to injuries suffered in a ski accident.

Question 3 • Why is this infection common only in certain geographical areas?

Answer 3 • Ticks is prevalent: Nantucket Island of Massachusetts Block Island in Rhode Island Long Island,Shelter Island, Fire Island in New York focal areas in Connecticut, Wisconsin, Minnesota • Between May~August • In Nantucket →60% of deer mice are infected with B. microti.

Question 4 • Which other infections are transmitted by the same vector?

Answer 4 • Vector→Ticks (壁蝨) • The tick of may simultaneously transmit 1.Borrelia burgdorferithe→Lyme disease 2.Ehrlichia (Anaplasma) species→ehrlichiosis (Rickettsia, Ehrlichia) =>Those coinfections may make clinical illness more severe and warrant special therapy.

Question 5 • Describe the life cycle of this parasite.

Answer 5

Ticks ingest Babesia while feeding, and the parasite multiplies within the tick's gut wall. The organisms then spread to the salivary glands; their inoculation into a vertebrate host by a tick larva, nymph, or adult completes the cycle of transmission. Asexual reproduction of Babesia within RBCs1 produces two or four parasites

Question 6 • In which other manner may this infection be transmitted?

Answer 6 • Blood transfusion • Acquired perinatally

Question 7 • How do infections with this parasite in other geographical areas differ from the case described here?

Answer 7 • The causative agent of babesiosis varies according to geographical region.

Question 8 • How may this infection be treated?

Answer 8 • Intact spleen→self-limiting although symptoms may persist for months . • Clindamycin(1.2 g Bid IV or 600 mg Tid po for 7~10 days) Quinine(650mgTid po for 7 days) • Atovaquone(750mg po Bid for 7~10 days) Azithromycin(600 mg po Qd for 7~10 days) • Severe infections (parasitemia/asplenic)→in addition to exchange transfusions • Occasionally, pulmonary edema may develop after initiation of therapy.

References • Harrison's Principles of Internal Medicine - 16th Ed. (2005) • Infectious disease the clinican’s guide to diagnosis treatment and prevention 2005

Case presentation