Gastric and intestinal myiasis due to Ornidia obesa ( Diptera : Syrphidae ) in humans . First report in colombia Miasis gástrica e intestinal por Ornidia obesa ( Diptera : Syrphidae ) en humanos . Primer reporte en Colombia

Myasis are parasitic infestations of animals and humans tissues and is caused by fly larvae. This kind of infestation has Public Health importance. In the Colombian biomedical literature the reports about myiasis in humans are scarce. In this paper, we report two cases of patients with gastrointestinal myiasis where the etiologic agents involved were Ornidia obesa and Ornidia sp (Diptera: Syrphidae). The taxonomic identification of the larvae was done at the Colombian Institute of Tropical Medicine and taxonomic confirmation was done at the laboratory of medicine veterinary and Zoology of Sao Pablo University. These two cases of myiasis are of first report in Colombia


INTRODUCCIÓN
Las miasis son infestaciones parasitarias de tejidos y órganos de animales y humanos o c a s i o n a d a s p o r l a r va s d e m o s c a s .L a infestación puede localizarse en piel, tejidos necróticos y en cavidades como fosas nasales, tracto gastrointestinal y genitourinario (1).

INTRODUCTION
Myiasis is parasitic infestation of animal and human tissues and organs caused by fly larvae.The infestation can be localized on the skin, necrotic tissues and in cavities such as the nostrils, gastrointestinal tract and genitourinary tract (1).
Myiasis can be classified according to the affected tissues or anatomical region as cutaneous or systemic.As for the latter, although its initial location is the skin, it can migrate to the gastric, intestinal, rectal, urinary, auricular and ophthalmic tissues (2), causing dermal, cutaneous or subdermal myiasis; Urogenital myiasis; Gastrointestinal or enteral myiasis; Ocular myiasis; Nasopharyngeal myiasis; Etc.(3,4).
According to the degree of parasitism, myiasis can be classified as obligatory when larvae feed exclusively on living tissues, optional when larvae require necrotic and accidental tissues when they are caused by free diopters, but under certain circumstances can be ingested by the host and develop in it accidentally (1,(5)(6)(7).
The most common etiological agents are larvae from genus: Sarcophaga, Dermatobia, Oestrus, Gasterophilus, Cochliomya, Lucilia, Chrysomya and Musca (8).Larvae are initially fed for a given time on living or dead tissues of the host, as well as on their organic fluids (7,8).
The most frequently associated diseases and risk factors for myiasis are: exposed ulcers, hemorrhoids, cutaneous bacterial infections, heavily exuding wounds, lack of personal grooming, farm animal raising, alcoholrelated behaviors such as insensitivity and sleeping outdoors, ingestion of contaminated food, abandoned individuals with diminished physical or mental functions (9,10).

CLINICAL CASE STUDY
The first case corresponds to a 70-yearold patient living in Medellín, Antioquia, who entered the hospital due to digestive problems: fetid feces, diarrhea, no mucus or blood, subjective fever, headache, general malaise, severe cramps.The patient reported that she sometimes saw the presence of a small animal moving inside her feces, which was extracted for laboratory examination.
The sample was sent to the Colombian Institute of Tropical Medicine (ICMT-CES) and identified as dipterous larvae in the third stage of El segundo caso se refiere a un paciente de 11 años, residente en Medellín, que consultó en varias ocasiones por dolor torácico y abdominal, disnea, heces diarreicas y sanguinolentas, y se le había hecho diagnóstico inicial de gastroenteritis infecciosa.Durante más de cinco meses estuvo eliminando parásitos por boca y nariz, a pesar de tratamiento con albendazol.development of the species Ornidia obesa (Diptera: Syrphidae) following the description of Montoya et al (11) (Figure 1).

Las larvas recolectadas fueron remitidas al laboratorio del
The second case refers to an 11-year-old patient living in Medellin, who consulted several times for chest and abdominal pain, dyspnea, bloody stools and diarrhea and an initial diagnosis of infectious gastroenteritis.For more than five months, the parasites were removed through his mouth and nose, despite treatment with albendazole.
The collected larvae were sent to the laboratory of the Colombian Institute of Tropical Medicine -CES where they were identified as larvae of Ornidia sp.Following the description by Montoya et al. (11), which does not allow to reach a species due to the L1 larval state (Figures 2-5).
The taxonomic identification of the larvae found in both patients was confirmed in the Laboratory of the Department of Preventive Veterinary Medicine and Animal Health of the Faculty of Veterinary Medicine and Animal Husbandry of the University of Sao Paulo (Dr.Marcelo Labruna).
Con respecto a las miasis accidentales por dípteros de la familia Syrphidae, se reportó por primera vez el caso clínico de una paciente chilena de 27 años de edad, la cual en un período menstrual presentó sensación de cuerpo extraño móvil en la región vaginal y luego expulsó larvas que fueron identificadas como larvas de tercer estado de Eristalis tenax can be classified into specific, semi-specific and accidental.Specific are those due to larvae that feed on living tissues, such as C. hominivorax, D. hominis.Semi-specific or secondary myiasis are those caused by larvae that survive feeding on necrotic tissues, for example: C. macellaria, Sarcophaga sp; And accidental myiasis, as its name implies, is installed by accident and caused especially by M. domestica, F. canicularis, and species of the family Syrphidae as Eristalis tenax and O. obesa, as the case reported in this work (2,10).
The most important human myiasis in our environment are caused by larvae of D. hominis and C. hominivorax (9)(10)(11).In other countries such as Chile and Brazil there are reports of the presence of accidental myiasis by E. tenax and O. obesa (10,12).
It is important to emphasize that the larvae of syrphids have different eating habits and adults have a main ecological function of pollination.
The results of the studies in Colombia indicate a wide distribution of syrphids species which,    as reported in this work and in literature, may produce accidental myiasis in humans (11).
Regarding accidental myiasis caused by Diptera of the Syrphidae family, the clinical case of a 27-year-old Chilean female patient was reported for the first time, who in a menstrual period presented a sensation of foreign body moving in the vaginal region and then expelled Larvae that were identified as third instar larvae of Eristalis tenax (Diptera: Syrphidae) (10).
Similarly, intestinal myiasis by O. obesa larvae was reported in Brazil in an eight-year-old girl who was taken to the hospital with hyperthermia, abdominal pain and intestinal obstruction.In the physical examination two larvae and one pupa of this species were found.According to the medical report, the patient may have consumed food contaminated with eggs or larvae (13).For the case in Colombia, no records of this type of accidental myiasis by O. obesa were found, being this the first reported case.
In different reports of myiasis (2,4), the patients present important immunocompromised conditions, among others, advanced age and malnutrition; as well as intrinsically attractive factors for the oviposition of flies, such as the presence of tissues with abundant protein rich exudates, that also serve as chemotactic agents for flies (3,4).
For the case of the type of myiasis reported in the present study, these are not necessarily risk factors for accidental myiasis.Proper management of organic waste and food handling must be effective in the prevention of this type of cases.
Finally, it is pertinent to draw attention to the treatment of myiasis.Oral ivermectin administration is based on diverse scientific evidence (9,12), in addition to assisting in the control of larvae in difficult-to-access cavitary myiasis.However, it is important to emphasize the importance of mechanically monitoring and extracting the larvae, as these could invade healthy tissue and cause significant damage, including intense pain and deformation (4).This possibility of invasion, in turn, depends on the dipterous species involved in the infestation (3,4).

Acknowledgment
To Dr. Marcelo Bahía Labruna Laboratory Director of the Department of Preventive Veterinary Medicine and Animal Health of the Faculty of Veterinary Medicine and Animal Husbandry of the University of Sao Pablo for confirmation in the identification of the larvae.
En diferentes reportes de miasis (2,4), l o s p a c i e n t e s p r e s e n t a n i m p o r t a n t e s condicionantes de inmunocompromiso, entre otros, edad avanzada y desnutrición; además de factores intrínsecamente atrayentes para la oviposición de las moscas, tales como la presencia de tejidos con abundantes exudados ricos en proteínas que, además, sirven como agentes quimiotácticos para las moscas (3,4).
Para el caso del tipo de miasis reportada en el presente trabajo, esos no necesariamente son factores de riesgo condicionantes para la presentación de las miasis accidentales.Un adecuado manejo de los desechos orgánicos y de la manipulación de alimentos, deben ser efectivos para la prevención de este tipo de casos.

Agradecimientos
Al Dr. Marcelo Bahía Labruna Director del Laboratorio del Departamento de Medicina Veterinaria Preventiva en Salud Animal de la Faculdad de Medicina Veterinaria y Zootecnia Universidad de Sao Pablo por la confirmación en la identificación de las larvas.