Efficacy of oral fluralaner (Bravecto) against Tunga penetrans in dogs: A negative control, randomized field study in an endemic community in Brazil

Dynamics of Tunga penetrans infections and severity of associated morbidity among pigs during the dry season in rural Uganda

BACKGROUND

Tungiasis is a neglected tropical disease which is common in impoverished communities. In sub-Saharan Africa, it is caused by female sand fleas, Tunga penetrans, and pigs are amongst the major domestic animal reservoirs. Depending on the environment, tungiasis occurs throughout the year or preferentially in the dry seasons. This study investigated changes in sand flea abundance and associated morbidity in pigs during a dry season.

METHODS

Tunga penetrans lesions were counted and staged in 35 pigs amongst 22 households with at least one affected pig. Five weekly examinations were performed per animal during a dry season. Enrolment of pigs into the study lasted 17 days and examination was performed for 43 days. The severity score for acute pig tungiasis (SSAPT) was determined for each visit. Generalised linear mixed models (GLMM) were fitted on an absolute time scale to understand factors influencing the changes in abundance of sand flea lesions and SSAPT.

RESULTS

The prevalence/abundance of tungiasis-associated lesions increased from 57.1%/median 1 lesion at baseline to 71.4%/median 11 lesions after 4 weeks. In parallel, the median SSAPT increased from zero to six. The GLMM analyses fitting negative binomial models to the lesion numbers revealed that time had a linear and a quadratic effect for the viable stages 2 and 3a, and all viable sand flea stages in general with maximal abundance of sand fleas on days 17-18, 33 and 35 from the beginning of the study, respectively. The model for the total number of sand flea lesions, which included dead and excoriated sand fleas, showed the same trend but the peak was not reached within the study period. The number of stage 3b lesions was unexpectedly low. The SSAPT increased linearly over time and was highly dependent on the initial number of sand fleas at enrolment.

CONCLUSIONS

There were increasing intensities of sand fleas and SSAPT in domestic pigs during the dry season. The ensuing environmental contamination by off-host stages of T. penetrans increases the risk of transmission to other susceptible hosts, including humans.

Efficacy of monthly treatment with oral fluralaner (Bravecto® 1-Month) against Tunga penetrans in dogs in Brazil: a randomized, double-blind, controlled field study

BACKGROUND

Tungiasis is a neglected tropical disease caused by the adult female sand flea (Tunga penetrans). Dogs are considered important reservoirs of T. penetrans in Brazil. The aim of this study was to determine the monthly insecticidal efficacy of a single oral administration of fluralaner at a dose of 10-18 mg/kg (Bravecto® 1-Month, also registered as Defenza® in some countries; MSD Animal Health) in dogs naturally infested with T. penetrans.

METHODS

This clinical trial was conducted in a rural community located in Ilhéus, Bahia, Brazil. A total of 64 dogs were selected and distributed in a completely randomized design between a treated group (TG) that received one single dose of Bravecto® 1-Month (Defenza®) and a negative control group (CG) that received no treatment. Each group was composed of 32 dogs. The evaluations took place on days 0, 7 ± 2, 14 ± 2, 21 ± 2, 28 ± 2, 35 ± 2, and 42 ± 2 post treatment, in which the dogs were inspected to evaluate the infestation stage and classify lesions associated with tungiasis. The primary efficacy was determined from the percentage of treated dogs free of fleas (stage II and III lesions) after administration of the formulation at each evaluation time. Secondary efficacy was based on the number of active lesions (stages II and III) in each group at each evaluation time. The clinical condition of the animals was defined based on the Severity Score for Acute Dog Tungiasis (SCADT), which is related to the number and severity of lesions.

RESULTS

The primary efficacy of the product was greater than 95.0% from days 7 to 21 and reached 100.0% between days 28 and 42, with a significant association between treatment and infestation decline (P < 0.025) between days 7 and 42. Secondary drug efficacy was greater than 99.9% from days 7 to 21, reaching 100.0% between days 28 and 42 (P < 0.05). The treated dogs also scored lower on the SCADT than the control animals did during the entire clinical evaluation period (P < 0.05).

CONCLUSIONS

A single administration of Bravecto® 1-Month (Defenza®) was effective in eliminating Tunga penetrans infestations, as well as in preventing parasitism for at least 42 days after treatment.

Use of sarolaner in the treatment of tungiasis in naturally infested dogs

Tungiasis is an endemic dermatological parasitic zoonosis in Latin America, caused by the sand flea Tunga spp. (Siphonaptera, Tungidae), which promotes intense discomfort, swelling, erythema, itching, pain, secondary bacterial infection, cellulitis and necrosis. Sarolaner has been used to control different ectoparasites, but there is no record of its use for the treatment of tungiasis in dogs. The objective of this study was to evaluate the effectiveness of sarolaner for the treatment dogs naturally infested by Tunga spp. kept in the same infested environment. Three of four animals were medicated with sarolaner orally with a single dose of 2 mg/kg, as recommended by the manufacturer, and one animal remained without medication. After 24 hours, the fleas from all four dogs were mechanically removed. The animals were reevaluated on days +15 and +30 to assess possible reinfestation. The medicated animals remained free of fleas, while the untreated animal had fleas on the days previously defined for reevaluation. We can thus conclude that the use of sarolaner is an effective choice for tungiasis treatment.

Efficacy of an oral formulation of afoxolaner and milbemycin oxime against Tunga penetrans in naturally infected dogs

BACKGROUND

The sand flea Tunga penetrans is one of the agents of tungiasis, an important parasitic skin disease affecting humans and several mammalian species. Tungiasis is mainly observed in disadvantaged rural and peripheral urban communities in Latin America and sub-Saharan Africa. The dog is a major reservoir of Tunga fleas. Hematophagous adult female Tunga spp. embed and grow in their host's epidermis and cause cutaneous inflammatory disorders. NexGard Spectra® is an orally administered endectocide for dogs, a co-formulation of the isoxazoline afoxolaner and the macrocyclic lactone milbemycin oxime. The objective of this study was to assess the efficacy of this product against canine tungiasis.

METHODS

A blinded, negative-controlled field trial was conducted in a Brazilian community known to be highly endemic for tungiasis. Sixty-six dogs naturally infected with live T. penetrans were randomly allocated to a treated group (44 dogs) and an untreated control group (22 dogs). In a first phase, dogs from the treated group were treated on days 0, 30, and 60. Efficacy was evaluated on the basis of the macroscopic parasitic skin lesions (Fortaleza classification) on days 7, 14, 21, 30, 45, 60, 75, and 90. In a second phase, to evaluate natural reinfections, all dogs were treated on day 90 and evaluated every 2 weeks thereafter until at least 30% of dogs were infected with live sand fleas.

RESULTS

During the first phase, efficacy (reduction in live sand fleas) of 92.4% was demonstrated on day 7. From day 14 until day 90, the efficacy of NexGard Spectra® was 100%. In the second phase, all dogs were free of live T. penetrans from 15 until 45 days after the day 90 treatment; 60 days post-treatment, 11% of dogs were reinfected, and 75 days post-treatment, 40% of dogs were reinfected.

CONCLUSIONS

NexGard Spectra® was demonstrated to be highly effective against canine tungiasis. In addition to an obvious beneficial effect on the health and welfare of the treated dog, the use of this product may have a one-health benefit on human cases by controlling the main reservoir of sand fleas.

Characterization of tungiasis infection and morbidity using thermography in Kenya revealed higher disease burden during COVID-19 school closures

BACKGROUND

Tungiasis is a neglected tropical skin disease caused by the sand flea Tunga penetrans. Female fleas penetrate the skin, particularly at the feet, and cause severe inflammation. This study aimed to characterize disease burden in two highly affected regions in Kenya, to test the use of thermography to detect tungiasis-associated inflammation and to create a new two-level classification of disease severity suitable for mapping, targeting, and monitoring interventions.

METHODS

From February 2020 to April 2021, 3532 pupils age 8-14 years were quasi-randomly selected in 35 public primary schools and examined for tungiasis and associated symptoms. Of the infected pupils, 266 were quasi-randomly selected and their households visited, where an additional 1138 family members were examined. Inflammation was assessed using infra-red thermography. A Clinical score was created combining the number of locations on the feet with acute and chronic symptoms and infra-red hotspots.

RESULTS

The overall prevalence of tungiasis among all the school pupils who were randomly selected during survey rounds 1 and 3 was 9.3% [95% confidence interval (CI): 8.4-10.3]. Based on mixed effects logistic models, the odds of infection with tungiasis among school pupils was three times higher in Kwale (coastal Kenya) than in Siaya [western Kenya; adjusted odds ratio (aOR) = 0.36, 95% CI: 0.18-0.74]; three times higher in males than in females (aOR = 3.0, 95% CI: 2.32-3.91) and three times lower among pupils sleeping in a house with a concrete floor (aOR = 0.32, 95% CI: 0.24-0.44). The odds of finding an infected person among the household population during surveys before the COVID-19 pandemic was a third (aOR = 0.32, 95% CI: 0.19-0.53) of that when schools were closed due to COVID-19 restrictions and approximately half (aOR = 0.44, 95% CI: 0.29-0.68) in surveys done after school re-opening (round 3). Infection intensity was positively correlated with inflammation as measured by thermography (Spearman's rho = 0.68, P < 0.001) and with the clinical score (rho = 0.86, P < 0.001). Based on the two-level classification, severe cases were associated with a threefold higher level of pain (OR = 2.99, 95% CI: 2.02-4.43) and itching (OR = 3.31, 95% CI: 2.24-4.89) than mild cases.

CONCLUSIONS

Thermography was a valuable addition for assessing morbidity and the proposed two-level classification of disease severity clearly separated patients with mild and severe impacts. The burden of tungiasis was considerably higher in households surveyed during COVID-19 restrictions suggesting underlying risks are found in the home environment more than in school.

Treatment of Animal Tungiasis: What’s New?

In tropical and subtropical countries, particularly in disadvantaged communities, tungiasis is a severe public health problem, which is often neglected by the authorities. The sand fleas Tunga penetrans, predominant in endemic areas, and Tunga trimamillata, whose cases in humans are less frequent, are the cause of this zoonosis. Domestic animals are potential reservoirs and disseminators of tungiasis, so controlling their infection would significantly advance the prevention of human cases. This literature review compiles the most recent studies and innovations in treating animal tungiasis. Studies of approaches to the treatment of animal tungiasis, as well as disease control and prevention, are described. Isoxazolines are highlighted as promising drugs to treat animal tungiasis, with high efficacy and pharmacological protection. The positive impacts of this discovery on public health are also discussed, since dogs are an essential risk factor for human tungiasis.