Challenges in differentiating cilia and protozoal flagella.

Sir,

We read with interest the case report of Lophomonas blattarum (LB) by Tyagi et al.[1] but would question some of the morphological characteristics in the figures provided.

First, in our experience, flagellated protozoa, such as LB, have the following morphological characteristics under light microscopy: a round to piriform shape 20–60 μm in diameter, a pair of flagella, or a tuft of flagella at the apical end of the cell, which are longer in the center that toward the sides, and a certain plasticity of the cytoplasm, containing coarse granules, and some phagocytic vacuoles, while on most occasions, the nucleus is not visible.[2] In both the pictures and the video provided by the authors, the morphology is somewhat different although we recognize that we have only seen a limited proportion of the views seen by the authors. Although one can observe some round to oval structures with filiform projections at one end, which have some similarity to flagella, in our opinion, they are more likely to be cilia, as they are very short, uniform, and arranged in a unidirectional pattern. In contrast, flagella are generally longer than cilia, irregular in form, and oriented in multiple directions. In our opinion, the rhythmic movement observed in the video provided by the authors corresponds better with bronchial ciliated cells as opposed to protozoal flagella.

Second, the presence of eosinophilia in peripheral blood samples is not pathognomic of protozoal infection. We recognize that eosinophilia appears frequently in human parasitosis and is a hallmark of some such as tropical pulmonary eosinophilia. However, the presence of protozoal in the lungs is generally not associated with extensive eosinophilia.[3] This patient may indeed have had eosinophilic lung disease, of which there are many including Löffler' syndrome, chronic eosinophilic pneumonia, Churg-Strauss syndrome, eosinophilic bronchitis, respiratory allergy, and allergic bronchopulmonary aspergillosis.[4]

Third, although flagellated protozoa are sensitive to metronidazole, it is also effective when treating a wide range of other bacterial diseases (mainly anaerobic infections) and could explain the positive therapeutic response in the reported case.[5]

Unfortunately, no cultures or molecular techniques have yet been developed that can specifically identify LB or other protozoa, and diagnosis is heavily dependent on experience and interpretation of features under light microscopy.

We would commend the authors for exploring the possibility of protozoal infection as we believe that protozoa are present in the lungs more often than is generally recognized.

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Conflicts of interest

There are no conflicts of interest.