This systematic review was carried out to identify all the available case reports and case series on oral myiasis. All the articles published from the year 1980 to 2017 were collected using the keywords “Diptera”, “Larvae”, “Maggots”, “Parasite”, “Ivermectin”. This search strategy was applied to key databases such as PubMed, and Google Scholar and the identified articles were independently reviewed by two reviewers, which was cross checked by the third reviewer. In addition, hand search of journals was completed for article retrieval. At this stage, all articles were collected and arranged chronologically. A total of 98 articles from PubMed, 18 from Google Scholar, and 2 from hand search were identified initially.

The articles were screened and selection of articles to be considered for review was based on inclusion and exclusion criteria.

Inclusion criteria:

Exclusion criteria:

After close scrutiny of their abstract, excluding the duplicates and based on the inclusion and exclusion criteria, 17 articles were finally included in our study. All selected articles were reviewed in full text after gaining access.

Based on the scrutiny of pre-existing records, the following articles were included in the study based on the inclusion and exclusion criteria [Table/Fig-1].

[Table/Fig-1]:

Inclusion and exclusion of the articles.

All the 17 case reports (18 cases) collected are summarised and tabulated in chronological order in [Table/Fig-2] [1,2,7,9-22].

The collected articles were analysed independently and their clinical features were summarised as follows,

Site: Gingiva in relation to anterior teeth and anterior part of the palate were the most commonly involved sites and the least involved sites were lip and floor of the mouth.

Gender: Among these 18 cases, 13 showed male predilection.

Age: It was more prevalent during second to fourth decade of life.

Distribution: Though worldwide in distribution, it is more predominantly seen in developing countries.

Associated disorder: Most of the patients presented with CNS disorders.

Number of larvae: The total number of larvae ranges from minimum of two larvae to maximum of hundreds of larvae.

Treatment: Surgical debridement under local anaesthesia.

Myiasis is defined as “infestation of live human and vertebrate animals with dipterous larvae that feed on the host’s dead or living tissue, liquid body substance or ingested food” by Zumpt [1]. It usually presents with painful ulcers along with facial edge and fever. Few cases also present with a crawling sensation and smelly discharge. Myiasis is a condition which was first identified and coined by Hope FW in 1840 [2] and later described by Laurence in 1909 [6]. Methods of infestation in humans may occur in two ways, either due to accidental inoculation of fly directly or by ingestion of infected material such as meat [23]. In most of the above mentioned cases, the location was predominantly involving the anterior palate and anterior gingiva which suggest a direct inoculation of fly in these tissues. In few other cases, it showed other sites involving floor of the mouth, mandibular molar region etc., which shows to have a possibility of ingestion of food contaminated with eggs or larvae of varying species, as it would be difficult for the fly to infest the tissues of molar region directly.

Myiasis of oral cavity is usually caused by flies of the order Diptera. The number of species causing infestation of oral cavity depends on the geographical distribution of the Dipteran species [8]. The life cycle of all these species involves four stages namely egg, larvae, pupae and finally the adult fly. The larvae stage involves three sub stages namely, first, second and third instar stage termed as maggots during which it reaches 11 to 15 mm in diameter. After the third instar stage, the maggot usually burrows for pupation and after 5 to 15 days during summer they emerge as adult flies. The average life span of an adult fly may range from 1 to 3 months. In humans, female flies lay over 500 eggs directly over the diseased tissue, the eggs hatch in less than 1 week and the life cycle is completed in about 2 weeks. The larvae obtain their nutrition from surrounding tissues and burrows deeper by forming a track or a path separating muco-periosteum from bone. The three main families causing myiasis includes Calliphoridae, Sarchophagidae and Oestridae. Majority of these species are larviparous i.e. they produce their younger ones in form of larvae [4].

Myiasis is a worldwide phenomenon, the prevalence of which is linked to the latitude and life cycle of the species. It frequently affects the rural areas infecting live stocks and pets such as dogs and cats. It is extremely rare in Europe and countries in northern hemisphere and more common in tropics and sub tropics [20]. The tropical climate of Brazil favours the growth of larvae [6]. A high rainfall may facilitate the maturation of the pupae. The flies responsible for this condition prefer warm and humid temperature, therefore myiasis is restricted to summer months in temperate zones and all year round in tropics. Rise in global trade, immigration and global warming will also increase the likelihood of myiasis, causing the flies to migrate to native areas or areas where they have been eradicated. It is also called as “traveller’s disease” as it is most commonly seen in travellers returning from the tropics and sub tropics [7].

It occurs in patients with poor oral hygiene, ill-fitting dentures, uncleaned prosthesis, advanced periodontal disease, at tooth extraction sites, thumb-sucking habits, seizures and incompetent lips. Alcoholism, senility, mental retardation, hemiplegia and mouth breathing during sleep may facilitate the development of oral myiasis [8]. Review of the available literature showed that it was most commonly seen in patients who needed assistance and were not able to take care of themselves and patients with CNS disorders namely cerebral palsy, neurological defect, learning disability etc., were more commonly affected. Mental illness refers to a wide range of mental health conditions i.e., disorders that affect mood, thinking and behaviour. When the ability to do normal functions is lost it leads to serious mental illness which is the main cause for poor hygiene which eventually acts as a cause for myiasis.

A slight male predilection is observed, the reasons may include adverse habits like smoking, tobacco chewing etc. which leads to poor oral hygiene, sleeping outdoors and spending more time outdoors. It is not confined to any particular age, it may occur in both children and older adults. It most commonly affects the anterior part of the palate followed by gingiva, being the less commonly affected site.

The larvae can be identified only after its isolation from the affected site. This helps to plan the treatment and also to promote preventive measures [4]. After removal, the larvae should be killed by immersing it into a very hot but not boiling water for 30 seconds which prevents decay and helps to maintain the natural colour. Later, it should be preserved in a solution of 70 to 95% ethanol or 70% isopropyl alcohol [4]. The use of formalin is contraindicated as it causes the tissue to harden making them difficult to process. Identification is the most challenging and demanding task. So a Specific knowledge about the morphological aspects of the larvae is necessary for its identification, which is a task usually done by trained entomologist [4].

The treatment of choice includes mechanical removal or surgical debridement of the larvae under local anaesthesia followed by antibiotic therapy. Ivermectin, a semi-synthetic, anthelminthic agent for oral administration. It is a macrolide antibiotic which is derived from the avermectins, a class of highly active broad spectrum, anti-parasitic agent isolated from Streptomyces avermitillis. It was initially used as a prophylactic treatment for filariasis and also for the treatment of scabies. It is generally administered at a dosage of 150 to 200 mg/kg. The trade name for ivermectin is STROMECTOL. The possible undesirable effect may include dermal eruption, dizziness, fever, migraine, muscular and joint pain [4].

Measures taken to control the fly have emerged as an alternative strategy to prevent the infestation. Basic sanitation and eradication of foci of adult fly proliferation are the initial steps in prevention of this disease. Adequate sanitation can be reached only when government, population and education programs work together. The use of screens and mosquito nets is essential to prevent flies from reaching the skin. Usage of insect repellents containing DEET (diethyltoluamide) can also be an alternative method. Other general precautions include covering wounds, avoiding falling asleep outdoors etc., [4].

Oral myiasis is relatively a rare entity of the oral cavity with very few reported and documented case studies. Hence further documentation of cases is required to comment elaborately on the inherent susceptibility of individuals with similar condition and associated complications of the disease. The eyes does not see what the mind does not know. Hence, the dentists, as well as the general public, should be educated about the potential implications of the disease throwing light on prevention and treatment aspects. The importance of early diagnosis should be emphasised upon. Frequent educational programmes will enable reaching out to the general public. Oral myiasis as a potential health hazard must be documented and elaborated upon, for only sound knowledge will help eradication of this preventable but substantially grave and morbid condition.