Current Trends in Entomology and Zoological Studies (ISSN: 2690-0114)

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Otobius megnini (Duges, 1844) Otoacariasis in a Horse from Tlahualilo, Durango, Mexico: A Case Report

Vicente Homero Gonzalez-Alvarez1, Josue Manuel de la Cruz-Ramos1, Sergio Orlando Yong-Wong1, Quetzaly Karmy Siller-Rodriguez2, Javier A. Garza-Hernandez3, Aldo Ivan Ortega-Morales4*

1Universidad Autónoma Agraria Antonio Narro, Posgrado en Ciencias en Producción Agropecuaria, Periférico Raúl López Sánchez s/n, Col. Valle Verde, C.P. 27059, Torreón, Coahuila, México

2Universidad Juarez del Estado de Durango, Facultad de Ciencias de la Salud, Calzada Las Palmas 1 y Sixto Ugalde, Col. Revolucion, C.P. 35050, Gomez Palacio, Durango, México

3Universidad Autonoma de Ciudad Juarez, Instituto de Ciencias Biomedicas, Laboratorio de Entomologia Medica, Anillo Envolvente y Estocolmo s/n, Zona Pronaf, C.P. 32310, Cd. Juarez, Chihuahua, Mexico.

4Universidad Autónoma Agraria Antonio Narro, Departmento de Parasitologia Periférico Raul Lopez Sanchez s/n, Col. Valle Verde, C.P. 27059, Torreon, Coahuila, México

*Corresponding author: Aldo Ivan Ortega-Morales, Departmento de Parasitologia, Universidad Autonoma Agraria Antonio Narro, Periferico Raul Lopez Sanchez s/n, Col. Valle Verde, C.P. 27059, Torreon, Coahuila, Mexico. Email:

Received Date: 17 April, 2018; Accepted Date: 11 June, 2018; Published Date: 20 June, 2018

Citation: Gonzalez-Alvarez VH, de la Cruz-Ramos JM, Yong-Wong SO, Siller-Rodriguez QK, Garza-Hernandez JA, et al.  (2018) Otobius megnini (Duges, 1844) Otoacariasis in a Horse from Tlahualilo, Durango, Mexico: A Case Report. Curr Trends Entomol Zool Stds: CTEZS-108. DOI: 10.29011/ CTEZS-108. 000008

1.  Abstract

This study reports the infestation of a horse by the tick Otobius megnini. A total of 82 specimens were collected from both ears during a routine consultation, and by morphological examination, all the specimens corresponded with the description of the ear tick. Studies are necessaries to determine the life cycle, the range of hosts, and the role in the transmission of diseases of public and veterinary concern by this tick in our region.

2.  Keywords: Argasidae; Ear tick; Horse; Otitis; Public health

1.   Introduction

Otoacariasis is defined as the affection of the ear canal, in which the causal agent is an arthropod classified in the subclass Acari [1]. Such as mites of the Democidae, Psoroptidae Sarcoptidae families or ticks grouped as Argasidae or Ixodidae [2]. Mites reported as a cause of mange in horses are Chorioptes equi, Psoroptes-equi and Sarcoptes scabiei var equi [3]. While the ticks commonly found in horses belong to the genera Amblyomma spp., Dermacentor spp., Ixodes spp., Rhipicephalus (Boophilus) spp. and Otobius megnini [4]. O. megnini as is a one host life cycle, in which the immature stages feed on blood inside the ear canal. As larva, it feeds for one to two weeks, while as nymph it feeds for one to seven months. When replete, nymphs drop off the host and crawl in to cracks of trees or buildings, where they melt into adults, mate, and lay eggs [5]. While the tick is in its parasitic stage, inside the ear canal, it causes pain which develops a variety of clinical signs, including head shaking, colic, emaciation, hyperesthesia, tremors and muscle spasms, and paralysis. Moreover, mechanical damage caused with its mouth parts provokes inflammation of the ear canal, tympanic membrane, and cause otitis interna, likewise secondary microbial infections of wounds could be developed [6]. Around the world, the presence of O. megnini in horses has been described in Argentina [7], Bolivia [8], Chile [9], and Sri Lanka [10]. While in Mexico. The first report of this soft tick comes from 1884 [11, Table1]. Notwithstanding, reports of this tick parasitizing horses in our country represents a gap in knowledge therefore, this study describes a case of otitis caused by the ear tick in a horse from Tlahualilo, Durango, Mexico.

2.  Case Report

On October 25/2017, a 10-year-old male horse was referred for consultation. The patient works in range land, co-existing with livestock and during the night is housed outdoors. The main signs found were restlessness and head shaking. At the examination of the ear canal, several foreign bodies were visually detected. As possible, all the material was manually extracted and deposited in a tray. Ear wax and debris were inspected carefully, and several arachnid-like arthropods were separated from the sample. The arthropods were deposited in appropriately labeled vials and transported to the Department of Parasitology of the Universidad Autonoma Agraria Antonio Narro for identification purpose. All the specimens were washed and under stereoscopic microscopy identified by adequate taxonomic keys [12].

3.  Results and Discussion

All the collected specimens corresponded with the description of the ear tick O. megnini [12]. A total of 82 specimens were collected (Table 2) and classified by life stage as described by Diyes and Rajakaruna [13], characteristics of the tick are described in Figure 1.

Treatment was initiated by removing ear wax and debris by mechanical cleaning of the ear. Chlorhexidine gluconate diluted in water was used as a final step of the ear cleaning, to prevent pathogen colonization. An acaricide in a petroleum jelly base was prescribed in order to control reinfestation of ticks. Furthermore, as O. megnini prefers cracks and crevices to hide and lay eggs, fumigation of the resting place was recommended. Madigan et al. [14] and Zarate-Ramos et al. [15] reported that this tick was associated with clinical manifestations including colic, hyperesthesia, hyper tonicity, muscle spasms, prolapse of the third eyelid, and tremors; however, otitis was not stated. Furthermore, in both cases, the horses recovered of clinical signs until they received treatment for the ear ticks. In this report, the patient did not manifest colic evidence, only head shaking, another clinical manifestation described by Madigan et al. [14]. The ear tick is commonly reported as a parasite of horses [7-10]. Severe infestations with O. megnini could block the ear canal and cause injuries with secondary bacterial infections, and nervous affection, causing balance dysfunctions commonly confused with neuromuscular disorders of another origin [16].

4.  Conclusion

Due to the putative role of O. megnini in the transmission of Coxiella burnetii, the Q fever agent [12] studies are necessaries to determine the life cycle, the range of hosts, and the role in the transmission of diseases of public and veterinary concern by this tick in our region.

5.  Acknowledgment

The authors thank the support of the Mexican National Council of Science and Technology (CONACYT) for the scholarship awarded for postgraduate studies.

Figure 1: Dorsal view of O. megnini specimens, a: unfed and engorged larvae; b: unfed, semi-engorged and engorged nymphs. The texture of integument with the characteristic spines can be observed.






Humans: Homo sapiens

Cats: Felis catus

Cattle: Bos spp.

Cervidae: Odocoileus spp.

Dogs: Canis lupus familiars

Donkeys: Equus asinus

Horses: Equus caballus

Mule: Equus asinus×Equus caballus

Sheep: Ovis aries

Baja California

Dry semi-arid


Dry semi-arid


Dry semi-arid


Warm sub-humid


Semi-arid, tempered sub-humid


Tempered sub-humid


Warm sub-humid


Semi-arid, tempered sub-humid


Semi-arid, warm sub-humid

Estado de México

Tempered sub-humid, warm sub-humid


Warm sub-humid tempered sub-humid


Warm sub-humid tempered sub-humid


Warm sub-humid, warm humid


Tempered sub-humid, warm sub-humid


Warm sub-humid, dry semi-arid


Dry semi-arid


Tempered sub-humid

Distrito Federal

Tempered sub-humid

*INEGI. Climatología. Available from:


Table 1: Characteristics on the distribution of O. megnini in México, adapted from Hoffman [11].









Semi engorded









Table 2: Categorization of the specimens recovered. 

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