ANSWER TO THE PHOTO QUIZ Philip A. Mackowiak, Section Editor

Of and Men (an Antology) (See page 78 for the Photo Quiz) Downloaded from https://academic.oup.com/cid/article/44/1/145/431911 by guest on 01 October 2021

Figure 1. A egg. The dark brownish egg is thick-walled and relatively small when compared with other helminthic eggs found in human feces (size, 40 mm ϫ 20 mm). A not-very-prominent operculum is marked by arrows (original magnification, ϫ20). Figure 2. A hatching Dicrocoelium dendriticum miracidium from the Diagnosis: Dicrocoelium dendriticum patient’s stool sample (original magnification, ϫ20). The adult trematode D. dendriticum, or lancet fluke, lives in the gall bladder and bile ducts of their final hosts (ruminants— their mammalian , metacercaria excyst from the ants and in particular, sheep). D. dendriticum eggs (figure 1), which are develop into young flukes, which migrate through the common passed in the feces of the final host, are swallowed by terrestrial bile duct into the liver. There, the adult dicrocoelia produce . In these primary intermediate hosts, miracidia develop eggs (figure 1), thus completing their complex life cycle [1]. into ceracaria within 3–4 months. A hatching miracidium from After ingestion of infected ants, humans may also become the patient’s stool sample is shown in figure 2. Subsequently, final hosts. This, however, is a quite rare phenomenon. In the the cercaria are excreted by the infected snails in “mucus balls.” vast majority of cases, the appearance of D. dendriticum eggs These mucus balls are eaten by ants, and the swallowed cercaria in human feces is due to ingestion of raw or half-cooked liver settle in the suboesophageal ganglion of the ants. This ironically of infected (e.g., sheep). For example, in a study in- named, so-called “brainworm” affects the behavior of its sec- volving 208 patients from Saudi Arabia with D. dendriticum ondary intermediate host dramatically; instead of returning eggs in stool samples, only 7 patients had true infection [2]. home when the daytime temperature falls, the “brainwashed” Similarly, in an additional study from Saudi Arabia involving ascends to the tip of a blade of grass. There, it clings in a 1196 parasitologically investigated patients, only 32 of 121 pa- state of tetania of its mandibular muscles to the vegetation and, tients with D. dendriticum eggs detected on microscopic ex- thus, becomes an easy victim for herbivorous sheep and , amination of stool samples had true dicrocoeliosis, as deter- the definite hosts of D. dendriticum. In the intestinal tract of mined by examination of additional stool samples obtained

ANSWER TO THE PHOTO QUIZ • CID 2007:44 (1 January) • 145 after 3 days of a liver-free diet [3]. In 77 egg-positive Swiss References patients, no true infection was diagnosed [4]. Such a spurious 1. Ducha´cek L, Lamka J. Dicrocoeliosis: the present state of knowledge infestation, or pseudoparasitism, seems unlikely in our patient, with respect to wildlife species. Acta Vet Brno 2003; 72:613–26. because she denied having eaten liver in the past. How- 2. el-Shiekh Mohamed AR, Mummery V. Human dicrocoeliasis: report on ever, examination of a control stool sample was not possible, 208 cases from Saudi Arabia. Trop Geogr Med 1990; 42:1–7. 3. Helmy MM, Al-Mathal EM. Human infection with Dicrocoelium den- because our patient was lost to follow-up. driticum in Riyadh district (Saudi Arabia). J Egypt Soc Parasitol 2003; Dicrocoeliasis is found in America, Asia, Europe, and 33:139–44. Northern Africa. In some parts of Central Europe, the preva- 4. Stahel E. Spurious infections by the small liver fluke (Dicrocoelium den- driticum) in Switzerland 1976–1980 [in German]. Schweiz Med Woch- 1 lence among sheep is 50% [1]. Even in the prehistoric human enschr 1981; 111:1159–62. population of Central Europe, D. dendriticum was present [5]. 5. Aspo¨ck H, Auer H, Picher O. Parasites and parasitic diseases in pre- Symptoms caused by D. dendriticum in humans include historic human populations in Central Europe. Helminthologia 1999; 36:139–45. chronic obstipation, chronic diarrhea [6], vomiting, hepato- 6. Rack J, Adusu E, Jelinek T. Humane Infektion mit Dicrocoelium den- megaly, jaundice, or colic pain due to biliary obstruction [7]. driticum. Dtsch Med Wochenschr 2004; 129:2538–40. Downloaded from https://academic.oup.com/cid/article/44/1/145/431911 by guest on 01 October 2021 It might be possible that the recurrent episodes of abdominal 7. Karadag B, Bilici A, Doventas A, et al. An unusual case of biliary ob- pain in our patient, which resulted in 2 laparoscopic exami- struction caused by Dicrocoelium dentriticum. Scand J Infect Dis 2005;37: 385–8. nations, were, in fact, caused by D. dendriticum, although this could not be proven because of the patient’s loss to follow-up. a Present affiliation: Dept. of Infectiology, Bavarian Health and Food Safety Authority, Ob- Recently, a patient with a case of chronic human infection erschleissheim, Germany. presenting with relapsing diarrhea, recurrent upper abdominal Reprints or correspondence: Dr. Andreas Sing, Bavarian Health and Food Safety Authority, pain, and weight-loss for 12 years has been reported [6]. Hu- Veterinaerstrasse 2, 85764 Oberschleissheim, Germany ([email protected]). man infections are usually treated with or Clinical Infectious Diseases 2007;44:145–6 2006 by the Infectious Diseases Society of America. All rights reserved. . 1058-4838/2007/4401-0026$15.00

Acknowledgments

We thank Karin Tybus for excellent parasitological assistance. Potential conflicts of interest. A.S.: no conflicts.

Andreas Singa Max von Pettenkofer Institut fu¨r Hygiene und Medizinische Mikrobiologie, Ludwig-Maximilians-Universita¨t Mu¨nchen, Munich, Germany

146 • CID 2007:44 (1 January) • ANSWER TO THE PHOTO QUIZ