A case of mixed infection with filariasis and visceral leishmaniasis.

Sir,

Leishmaniasis and lymphatic filariasis are important differential diagnoses in patients presenting with prolonged fever in Indian sub-continent.[1] Both the parasitic infections are endemic in many parts of India. Leishmania donovani, the parasite causing visceral leishmaniasis (Kala Azar) is a hemo-flagellate, transmitted by the bite of infected sand flies.[2] Wuchereria bancrofti, the most common agent causing lymphatic filariasis in India, is a nematode, transmitted by female Culex, Anopheles and Aedes mosquitoes.[3] Although both the parasites singly are commonly encountered in cases of pyrexia of unknown origin (PUO), especially in patients from endemic areas; mixed infection by both of these parasites is seldom reported. We are reporting a rare and interesting case of mixed infection with L. donovani and W. bancrofti. To the best of our knowledge, this is the second confirmed case of mixed infection by these two parasites.[4]

A 30-year-old male patient, resident of Bihar, India, presented with fever and loose motions for 2 months; and lump in the left side of the abdomen for one and ½ month duration. During the course of illness, he lost around 7 kg of body weight, became anorexic and asthenic. The patient's wife had lymphatic filariasis 2 years back and was treated with diethylecarbamazine. At the time of presentation the patient was febrile and there was severe pallor and angular stomatitis. On the examination of the abdomen, a massive hepato-splenomegaly was found. Rest of the clinical examination was within normal limits. The patient's preliminary blood investigations revealed pancytopenia with relative lymphocytosis. Ultrasonogram of the abdomen showed massive hepato-splenomegaly with minimal free fluid [Table 1].

Table 1

Preliminary investigations of the patient

Bone marrow aspiration was done on the 3rd day of hospitalization and was sent to the microbiology laboratory, All India Institute of Medical Sciences, New Delhi, India. Examination of Acridine-orange and Giemsa stained smears of bone marrow revealed the presence of amastigote forms of L. donovani - Leishman-Donovan bodies, grade 3+ [Figure 1]. Serum sample was tested for specific recombinant-Kinesin (rK)-39 anti-leishmania antibodies and was found to be positive (grade 4+).

Figure 1

Light microscopic (a) and fluorescence microscopic (b), photomicrograph showing Leishman-Donovan bodies

The quantitative buffy coat (QBC) examination was done to exclude malaria; which revealed the presence of motile microfilariae [Figure 2a]. A microfilarial count was done from the QBC, which came out to be 123/ml. Speciation of microfilaria, as W. bancrofti was done in QBC on the basis of distinct nuclei, cephalic space being as long as broad, tail end being pointed and free of nuclei, smooth body curves and absence of secondary kinks. In a Giemsa stained smear of concentrated blood specimen, speciation was confirmed [Figure 2b–d].

Figure 2

Light microscopic photomicrograph showing microfilaria of Wuchereria bancrofti (a-c), Photomicrograph showing microfilaria in quantitative buffy coat (d)

The patient was treated with intravenous amphotericin-B-1 mg/kg qid for 21st days for kala-azar and with diethylecarbamazine 6 mg/kg daily for 12 days for filariasis. During the course of treatment, kidney function tests, serum electrolytes and blood counts of the patient were monitored. Clinical improvement was observed after 3 days of initiation of treatment in the form of decreased fever, improved appetite and reduction in size of spleen. There was also improvement in blood counts and at the time of discharge, on 21st day, the patient's hemoglobin was 7.4 g%, total leucocyte count was 8400/μl with 64% polymorphs and 32% lymphocytes. Repeat bone marrow aspirate and peripheral blood were free of parasitic forms detected earlier. The patient was discharged in good condition after completion of treatment.

Mixed infections are an established entity in parasitology. Mixed gastrointestinal infections are very common. Mixed enteric parasitemias have been reported in the range of 5.5-32.8% from different geographical regions and patient populations.[56] Mixed blood borne infections of different species of malarial parasites, different filarial worms; and malaria and filariasis are known. This is because of the common mode of transmission in the case of former; and vector prevalence in the latter case. In malaria endemic areas, high prevalence (up to 45.5%) of mixed infections due to two or more Plasmodium species has been reported.[78] In a Nigerian study, 12.2% and 1.4% of patients with suspected filariasis have been reported to be infected with two and three species of filarial worms respectively.[9] Co-infections of malaria and filariasis are also common. A study from Guyana has reported 1.6% of patients with PUO attending malaria and filaria clinics to be having a mixed infection of both.[10] W. bancrofti and L. donovani are transmitted by different vectors (mosquitoes and sandflies respectively); both the vectors are found in Bihar state, which is the residence of the present patient. This fact re-emphasizes the role of environmental factors in parasitic infections.

There is a possibility that such mixed infections are under-diagnosed, as the mode of diagnosis of leishmaniasis and lymphatic filariasis are different. The use of potent techniques such as bone marrow smear examination, rK-39 antibody assay, along with QBC examination helped in detection of mixed infections in this case. In our experience, QBC analysis is a very sensitive technique to pick up presence of microfilaria as it enables detection in patients with low counts. In almost all positive cases, speciation and counting of microfilaria can be done with QBC examination. There are studies in the literature, which support the use of QBC examination for rapid and accurate detection of microfilariae in blood.[11] Nonetheless, QBC has the limitations that adjustment to the technique needs expertise and a fluorescence microscope is required. In the present case, considering the parasitic count and the clinical condition of the patient, it was decided to treat both the parasites.