Ivermectin plus diethylcarbamazine: an additive effect on early microfilarial clearance

Comparative Safety Surveillance of Triple (IDA) Versus Dual Therapy (DA) in Mass Drug Administration for Elimination of Lymphatic Filariasis in Kenya: A Cohort Event Monitoring Study

INTRODUCTION

Dual diethylcarbamazine and albendazole (DA) therapy is the standard mass drug administration (MDA) regimen for lymphatic filariasis in Kenya. Following the recent World Health Organization recommendation, Kenya piloted triple therapy with ivermectin, diethylcarbamazine, and albendazole (IDA) in MDA.

OBJECTIVE

We conducted a community-based, observational, cohort event monitoring study to compare the types, frequency, severity, and predictors of adverse events following dual versus triple therapy in 20,421 eligible residents.

METHODS

Residents in Kilifi (n = 10,010) and Mombasa counties (n = 10,411) received DA and IDA through MDA campaigns, respectively. Adverse events were actively monitored through house-to-house visits on days 1, 2, and 7 after MDA. Any clinical events reported before and after MDA were cross-checked and verified to differentiate pre-existing events from MDA-associated adverse events.

RESULTS

Overall, 5807 and 3102 adverse events were reported by 2839 and 1621 individuals in the IDA and DA groups, respectively. The incidence of experiencing one or more adverse events was significantly higher (p < 0.0001) in the IDA group (27.3%; 95% confidence interval [CI] 26.4-28.2) than in the DA group (16.2%; 95% CI 15.5-16.9). Dizziness (15.9% vs 5.9%) and drowsiness (10.1% vs 2.6%) were the most common adverse events and significantly higher in the IDA group compared with the DA group (p < 0.0001). Most adverse events were mild or moderate with a few severe cases (IDA = 0.05%; 95% CI 0.35-0.78, DA = 0.03%; 95% CI 0.14-0.60). Female sex, obesity, taking three or more diethylcarbamazine or ivermectin tablets, and having pre-existing clinical symptoms were significant predictors of adverse events following IDA treatment.

CONCLUSIONS

Ivermectin, diethylcarbamazine, and albendazole as a combination is as safe and well tolerated as DA to use in MDA campaigns with no serious life-threatening adverse events. Systemic mild-to-moderate adverse events with a few severe cases and transient adverse events are more common with IDA treatment than with DA treatment. Hence, integrating pharmacovigilance into a MDA program is recommended for the timely detection and management of adverse events.

Adverse events following single dose treatment of lymphatic filariasis: Observations from a review of the literature

Background

WHO’s Global Programme to Eliminate Lymphatic Filariasis (LF) uses mass drug administration (MDA) of anthelmintic medications to interrupt LF transmission in endemic areas. Recently, a single dose combination of ivermectin (IVM), diethylcarbamazine (DEC), and albendazole (ALB) was shown to be markedly more effective than the standard two-drug regimens (DEC or IVM, plus ALB) for achieving long-term clearance of microfilaremia.

Objective and methods

To provide context for the results of a large-scale, international safety trial of MDA using triple drug therapy, we searched Ovid Medline for studies published from 1985–2017 that reported adverse events (AEs) following treatment of LF with IVM, DEC, ALB, or any combination of these medications. Studies that reported AE rates by treatment group were included.

Findings

We reviewed 162 published manuscripts, 55 of which met inclusion criteria. Among these, 34 were clinic or hospital-based clinical trials, and 21 were community-based studies. Reported AE rates varied widely. The median AE rate following DEC or IVM treatment was greater than 60% among microfilaremic participants and less than 10% in persons without microfilaremia. The most common AEs reported were fever, headache, myalgia or arthralgia, fatigue, and malaise.

Interpretation

Mild to moderate systemic AEs related to death of microfilariae are common following LF treatment. Post-treatment AEs are transient and rarely severe or serious. Comparison of AE rates from different community studies is difficult due to inconsistent AE reporting, varied infection rates, and varied intensity of follow-up. A more uniform approach for assessing and reporting AEs in LF community treatment studies would be helpful.

WHO’s Global Programme to Eliminate Lymphatic Filariais (LF) supports annual mass drug administration to over 400 million people in LF-endemic areas each year. Two drug combinations (either DEC or ivermectin, given with albendazole) have been recommended in most endemic areas. With the exception of well-described serious adverse events (AEs) occurring in patients with high level loiasis, severe AEs due to these medications are extremely rare. Mild to moderate AEs, however, are common, particularly in patients with active filarial infection. In this manuscript we synthesize published data on AEs following single-dose treatment of LF with ivermectin, DEC, or albendazole. This provides a background against which to compare the safety of triple drug therapy (ivermectin, DEC, and albendazole) recently endorsed by WHO, and provides a useful context for evaluating safety of new treatments for LF. The compiled data illustrate that transient, mild to moderate AEs following single-dose LF treatment are common in microfilaremic patients and are much less common in amicrofilaremic patients. They also show that passive surveillance for post-treatment AEs underestimates AE incidence and suggest that adherence to common reporting standards would improve the usefulness of AE reporting in filariasis studies.

Ivermectin susceptibility and sporontocidal effect in Greater Mekong Subregion Anopheles

Background

Novel vector control methods that can directly target outdoor malaria transmission are urgently needed in the Greater Mekong Subregion (GMS) to accelerate malaria elimination and artemisinin resistance containment efforts. Ivermectin mass drug administration (MDA) to humans has been shown to effectively kill wild Anopheles and suppress malaria transmission in West Africa. Preliminary laboratory investigations were performed to determine ivermectin susceptibility and sporontocidal effect in GMS Anopheles malaria vectors coupled with pharmacokinetic models of ivermectin at escalating doses.

Methods

A population-based pharmacokinetic model of ivermectin was developed using pre-existing data from a clinical trial conducted in Thai volunteers at the 200 µg/kg dose. To assess ivermectin susceptibility, various concentrations of ivermectin compound were mixed in human blood meals and blood-fed to Anopheles dirus, Anopheles minimus, Anopheles sawadwongporni, and Anopheles campestris. Mosquito survival was monitored daily for 7 days and a non-linear mixed effects model with probit analyses was used to calculate concentrations of ivermectin that killed 50% (LC₅₀) of mosquitoes for each species. Blood samples were collected from Plasmodium vivax positive patients and offered to mosquitoes with or without ivermectin at the ivermectin LC₂₅ or LC₅ for An. dirus and An. minimus.

Results

The GMS Anopheles displayed a range of susceptibility to ivermectin with species listed from most to least susceptible being An. minimus (LC₅₀ = 16.3 ng/ml) > An. campestris (LC₅₀ = 26.4 ng/ml) = An. sawadwongporni (LC₅₀ = 26.9 ng/ml) > An. dirus (LC₅₀ = 55.6 ng/ml). Mosquito survivorship results, the pharmacokinetic model, and extensive safety data indicated that ivermectin 400 µg/kg is the ideal minimal dose for MDA in the GMS for malaria parasite transmission control. Ivermectin compound was sporontocidal to P. vivax in both An. dirus and An. minimus at the LC₂₅ and LC₅ concentrations.

Conclusions

Ivermectin is lethal to dominant GMS Anopheles malaria vectors and inhibits sporogony of P. vivax at safe human relevant concentrations. The data suggest that ivermectin MDA has potential in the GMS as a vector and transmission blocking control tool to aid malaria elimination efforts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1923-8) contains supplementary material, which is available to authorized users.

Imported bancroftian filariasis: diethylcarbamazine response and benzimidazole susceptibility of Wuchereria bancrofti in dynamic cross-border migrant population targeted by the National Program to Eliminate Lymphatic Filariasis in South Thailand

The implementation on the Thailand-Myanmar border of annual mass drug administration (MDA) of a single 6 mg/kg dose of diethylcarbamazine (DEC) plus 400mg albendazole, part of the National Program to Eliminate Lymphatic Filariasis (PELF), has been challenging. In particular, chain migration of cross-border Myanmar workers at risk for nocturnally periodic Wuchereria bancrofti infection can lead to imported bancroftian filariasis (IBF) in Thailand. IBF is targeted for multiple-dose MDA with 300 mg DEC, in addition to what is recommended by the World Health Organization (WHO). The dynamic Myanmar migrants in Phang-nga, southern Thailand were sampled to test whether the responsible W. bancrofti has a genetic predisposition of benzimidazole exposure, and IBF exhibits DEC susceptibility. The long-term migrants had more access to DEC. IBF in W. bancrofti antigenemic (microfilaremic vs. amicrofilaremic) short-term migrants exhibited susceptibility to a 300-mg single-dose DEC treatment. During the course of a 3-month follow-up, antigenemia was significantly reduced, but microfilaremia was fluctuated. Surprisingly, a newly recognized Mansonella infection co-existing among W. bancrofti-affected Myanmar migrants elicited microfilaremia clearance within a month after treatment. As a result of the presence of genetically stable W. bancrofti beta-tubulin (Wbtubb) gene responsible for benzimidazole susceptibility, IBF did not possess a genetic predisposition for benzimidazole exposure. Point mutations at positions Phe167Tyr and Phe200Tyr were not detected by Wbtubb locus-specific nested PCR and sequencing. This study has the potential to help guide not only the Thai/Myanmar PELF surveillance and monitoring of mass treatment impacts on W. bancrofti, but also the other endemic countries allied with the Global Program to Eliminate Lymphatic Filariasis (GPELF).

A successful outcome of gross haematuria treated with diethylcarbamazine and ivermectin

Gross haematuria caused by lymphatic filariasis has been rarely reported. An adult woman living in a filarial-endemic area presented at a hospital in Orissa, India, in July 2004, with painless gross haematuria without any associated symptoms, such as dysuria, abdominal pain and fever. Urine microscopy revealed many erythrocytes and the immunochromatographic test was positive for filarial antigenaemia. After excluding other causes of haematuria, the patient was treated with a standard dose of diethylcarbamazine for 12 days and a single dose of ivermectin (200 microg/kg) and responded well without any recurrence for 2 years of follow-up.

Efficacy and safety of drug combinations in the treatment of schistosomiasis, soil-transmitted helminthiasis, lymphatic filariasis and onchocerciasis

This review concerns the efficacy and safety of combinations of various drugs, including albendazole (ALB), diethylcarbamazine (DEC), ivermectin (IVM), mebendazole and praziquantel (PZQ). There were no significant pharmacokinetic interactions when ALB-PZQ, ALB-DEC, ALB-IVM or ALB-IVM-PZQ were co-administered. ALB did not add to the cure rate of PZQ in the treatment of Schistosoma japonicum, S. mansoni and S. haematobium. ALB and DEC in combination and alone were ineffective against S. haematobium infections. No combinations (ALB-PZQ, ALB-IVM and ALB-DEC) were superior to ALB against Ascaris lumbricoides and hookworm infections, whilst IVM, but not PZQ or DEC, added to the effect of ALB in the treatment of Trichuris trichiura. Results with ALB added to single-drug therapy with IVM or DEC against lymphatic filariasis were inconclusive, but DEC and IVM in combination appeared to be superior to DEC or IVM alone. None of the drug combinations against lymphatic filariasis showed more adverse reactions than single-drug therapy. In onchocerciasis patients, ALB and IVM were safe in those also infected with lymphatic filariasis, but were not superior to IVM alone. Existing policies are based on limited knowledge. Well conducted, comparative, randomised controlled studies would greatly aid in the future use of these drug combinations.

Mass chemotherapy options to control lymphatic filariasis: a systematic review

Understanding the efficacy of microfilaricidal drugs is important in guiding the global programme for the elimination of lymphatic filariasis as a public-health problem. We did a systematic review of the available literature to determine which currently available drug intervention most effectively decreases circulating Wuchereria bancrofti microfilaria in individuals and populations. 57 randomised studies of drug efficacy were identified. Data were combined and compared using weighted mean effect estimates taking into account the longitudinal nature of the data. Combined treatment with diethylcarbamazine plus ivermectin, diethylcarbamazine plus albendazole, and ivermectin plus albendazole resulted in average microfilarial intensity decreases that were 0.7%, 4.6%, and 12.7% of the pre-treatment values, respectively. Drug combinations containing diethylcarbamazine were the most effective against microfilarial prevalence and intensity relative to single drugs or other combinations. The relative efficacies of drug combinations have not been well documented from existing studies and therefore limit the application of evidenced-based recommendations for chemotherapy-based interventions to control lymphatic filariasis. These results provide valuable estimates of drug effect using existing data, but highlight the need for more comprehensive comparative drug studies.

Chemotherapy for lymphatic filariasis: progress but not perfection

Currently, only three drugs are used to control and treat the mosquito-borne parasitic disease lymphatic filariasis: diethylcarbamazine, ivermectin (Mectizan) and albendazole (Zentel). All interrupt transmission by eliminating microfilaria, the parasite stage that is responsible for transmission between hosts, but do not reliably kill the adult worms that are responsible for much of the pathology seen in the disease. There is an urgent need to develop drugs that will reliably kill adult worms and several compounds are under-going in vitro and animal testing. An alternative strategy - that of targeting symbiont bacteria within the parasite - has also shown promising results.

Treatment of Brugia timori and Wuchereria bancrofti infections in Indonesia using DEC or a combination of DEC and albendazole: adverse reactions and short-term effects on microfilariae

Filariasis caused by Brugia timori and Wuchereria bancrofti is an important public health problem on Alor island, East Nusa Tenggara, Indonesia. To implement a control programme, adverse reactions and short-term effects on the microfilaria (mf) density were studied following a divided dose of diethylcarbamazine (DEC, 6 mg/kg body weight - 100 mg on day 1 and the rest on day 3) or a single dose of DEC (6 mg/kg body weight on day 3) and albendazole (Alb, 400 mg). In order to define the most appropriate regimen, 30 persons infected with B. timori were treated in the hospital and results were compared with those obtained from the treatment of 27 persons infected with W. bancrofti. Adverse reactions consisted of systemic reactions such as fever, headache, myalgia, itching and local reactions such as adenolymphangitis. Fever experienced by a number of patients in both treatment groups generally occurred 12-24 h after drug administration and lasted up to 2 days. Adenolymphangitis tended to occur later and was resolved within 4 days. The number of W. bancrofti patients suffering from adverse reactions was lower and the reactions were milder than those of the B. timori patients. There was no difference in adverse reactions between DEC alone and DEC-Alb treatment for either infection. The geometric mean mf count decreased on day 7 in the B. timori infected patients from 234 mf/ml in the DEC group and from 257 mf/ml in the DEC-Alb group to 7 and 8 mf/ml, respectively. The mf densities of the W. bancrofti infected patients decreased on day 7 from 214 mf/ml in the DEC group and from 559 mf/ml in the DEC-Alb group to 15 and 14 mf/ml, respectively. Our data indicate that the microfilaricidal effect of the drugs is achieved more rapidly for B. timori, which is associated with more adverse reactions than W. bancrofti. In addition, 111 B. timori infected persons were treated in the community with DEC-Alb in one selected village. The adverse reactions and the reduction of mf density was similar to the findings of the hospital-based study. In this group, there was a strong correlation of mf density with the frequency and severity of adverse reactions. The addition of Alb resulted in no additional adverse reactions compared with DEC treatment alone and can also be used for the treatment of B. timori infection. In Indonesia, where the prevalence of intestinal helminths is high, the use of a combination of DEC and Alb to control lymphatic filariasis may also have impact on the control of intestinal helminths.

Perturbations in eosinophil homeostasis following treatment of lymphatic filariasis

Treatment of patients with patent Wuchereria bancrofti infection results in an acute clinical reaction and peripheral eosinophilia. To investigate the dynamics of the eosinophil response, changes in eosinophil activation and degranulation and plasma levels of eosinophil-active chemokines and cytokines were studied in 15 microfilaremic individuals in south India by sequential blood sampling before and after administration of 300 mg of diethylcarbamazine (DEC). Clinical symptoms occurred within 24 h. Plasma interleukin-5 (IL-5) and RANTES levels peaked 1 to 2 days posttreatment, preceding a peak peripheral eosinophil count at day 4. Major basic protein secretion from eosinophils paralleled IL-5 secretion, while levels of eosinophil-derived neurotoxin peaked at day 13 after treatment. Expression of the activation markers HLA-DR and CD25 on eosinophils rose markedly immediately after treatment, while expression of VLA-4 and alpha4beta7 showed an early peak within 24 h and a second peak at day 13. Thus, the posttreatment reactions seen in filarial infections can be divided into an early phase with killing of microfilariae, clinical symptomatology, increases in plasma IL-5 and RANTES levels, and eosinophil activation and degranulation and a later phase with expression of surface integrins on eosinophils, recruitment of eosinophils from the bone marrow to tissues, and clearance of parasite antigen.

Epidemiology and immunopathology of bancroftian filariasis

Human lymphatic filariasis affects 120 million people worldwide. Although the disease is considered to be potentially erradicable by the World Health Organization, comprehensive studies on epidemiological aspects as well as mechanisms of pathology development are still premature. The following review summarizes currently available data on these topics and ends by discussing the latest control strategies.

Ivermectin for the chemotherapy of bancroftian filariasis: a meta-analysis of the effect of single treatment

The efficacy and safety of ivermectin in the treatment of filariasis due to Wuchereria bancrofti was assessed by a meta-analysis of the results from 15 published clinical trials. Seven hundred and forty-eight microfilaraemic patients were enrolled in 7 dose-finding and 8 comparative studies. Administered as a single dose, ivermectin induced nearly complete clearance of microfilariae from the blood from the first day to 30 days post-treatment, followed by gradual recurrence of microfilaraemia and increase in its intensity. Higher doses of ivermectin showed greater clearance effects and maintained lower microfilaraemia levels for a longer time. The adverse reactions caused by the drug were flu-like, transient, generally mild and well tolerated by patients. The frequency and intensity of adverse reactions were strongly associated with pretreatment microfilaria counts in the blood, but independent of dose. The findings of the meta-analysis suggest that ivermectin given at a single annual dose of 200 micrograms/kg body weight or higher, whether or not in combination with DEC, has great potential for therapeutic strategies to control bancroftian filariasis.

Development of a competitive enzyme-linked immunosorbent assay for diethylcarbamazine

A sensitive and reproducible competitive enzyme-linked immunosorbent assay (ELISA) for the determination of the concentration of diethylcarbamazine (DEC) in biological fluids was developed. Since DEC has no functional group to conjugate with bovine serum albumin (BSA), N-(2-aminoethyl)-N-ethyl-4-methyl-1-piperazinecarboxamide (DEC-NH2) was first synthesized. This compound was then converted to carboxyl DEC (DEC-COOH) and conjugated to BSA and to poly-L-lysine for use as immunogen and solid-phase marker, respectively. The competitive ELISA was conducted by simultaneously incubating DEC with mouse anti-DEC antiserum over DEC-poly-L-lysine solid phase. Subsequently, the binding of anti-DEC antibody was detected by using sheep anti-mouse IgG peroxidase conjugate as a tracer. The reliability, determined by the coefficient of variation for inter and intra-assay, was satisfactory. The cross-reactivities of anti-DEC antibodies with DEC metabolites, related compounds and ivermectin were negligible. Using this assay, DEC levels were easily determined in serum of Mongolian jirds (Meriones unguiculatus) up to 4 hours following a single dose of DEC citrate base (100 mg/kg of body weight) via intraperitoneal route.

A polymerase chain reaction assay for the detection of Wuchereria bancrofti in blood samples from French Polynesia

A polymerase chain reaction (PCR) assay based on a highly repeated deoxyribonucleic acid (DNA) sequence found in Wuchereria bancrofti (the SspI repeat) has been developed to address the shortcomings of traditional diagnostic methods. In this field study in a W. bancrofti endemic region of French Polynesia, 373 human blood samples were collected and 100 microL of blood were screened by the SspI PCR assay and 1 microL by membrane filtration. The SspI PCR assay detected 99 of 113 blood samples in which microfilariae had been detected by filtration (sensitivity of 88%) with a specificity of 100%. All the samples missed by the SspI PCR assay had less than 8 microfilariae per mL of blood. To evaluate the efficacy of screening larger blood samples by PCR, both 100 microL and 500 microL samples from 50 patients with very low-level microfilaraemia were screened by the SspI PCR assay; the sensitivity increased from 60% to 84% when using the larger volume of blood. Finally, an enzyme-linked immunosorbent assay-based version of the SspI PCR assay was used to screen blood from 12 patients following treatment with diethylcarbamazine, ivermectin, or both. These results showed that the PCR assay closely paralleled the presence or absence of microfilariae in the blood and that no increase in the DNA level was seen immediately following drug treatment.

Double-blind controlled trial of a single dose of the combination ivermectin 400 micrograms/kg plus diethylcarbamazine 6 mg/kg for the treatment of bancroftian filariasis: results at six months

In 1993, a three-arm double-blind controlled trial was implemented in French Polynesia to compare the tolerance and efficacy of a single dose of the combination ivermectin (IVR) 400 micrograms/kg plus diethylcarbamazine (DEC) 6 mg/kg vs. IVR 400 micrograms/kg alone vs. DEC 6 mg/kg alone, for treatment of Wuchereria bancrofti carriers. Of the 57 treated male patients in whom microfilaria (mf) densities ranged from 22 to 4709 mg/mL, 3 groups of 19 were randomly selected and allocated to one of the 3 treatments. Side effects were experienced by 34 patients (60%), but none suffered a severe reaction. Grade of reaction did not differ between treatment group, but was significantly correlated with the pretreatment mf density. Six months after treatment, 26%, 32% and 53% of patients were amicrofilaraemic in the DEC, IVR and IVR+DEC groups, respectively. Mf levels were 6.3%, and 3.1% and 1.0% of the pretreatment level, respectively, significantly lower in the IVR+DEC group than in both the IVR and DEC comparison groups. The combination IVR+DEC showed promise in term of sustained mf decrease, and could be an effective alternative for lymphatic filariasis control programmes.