Analysis of Iophenoxic Acid Analogues in Small Indian Mongoose (<em>Herpestes Auropunctatus</em>) Sera for Use as an Oral Rabies Vaccination Biological Marker

Abstract

The small Indian mongoose (Herpestes auropunctatus) is a reservoir of rabies virus (RABV) in Puerto Rico and comprises over 70% of animal rabies cases reported annually. The control of RABV circulation in wildlife reservoirs is typically accomplished by a strategy of oral rabies vaccination (ORV). Currently no wildlife ORV program exists in Puerto Rico. Research into oral rabies vaccines and various bait types for mongooses has been conducted with promising results. Monitoring the success of ORV relies on estimating bait uptake by target species, which typically involves evaluating a change in RABV neutralizing antibodies (RVNA) post vaccination. This strategy may be difficult to interpret in areas with an active wildlife ORV program or in areas where RABV is enzootic and background levels of RVNA are present in reservoir species. In such situations, a biomarker incorporated with the vaccine or the bait matrix may be useful. We offered 16 captive mongooses placebo ORV baits containing ethyl-iophenoxic acid (et-IPA) in concentrations of 0.4% and 1% inside the bait and 0.14% in the external bait matrix. We also offered 12 captive mongooses ORV baits containing methyl-iophenoxic acid (me-IPA) in concentrations of 0.035%, 0.07% and 0.14% in the external bait matrix. We collected a serum sample prior to bait offering and then weekly for up to eight weeks post offering. We extracted Iophenoxic acids from sera into acetonitrile and quantified using liquid chromatography/mass spectrometry. We analyzed sera for et-IPA or me-IPA by liquid chromatography-mass spectrometry. We found adequate marking ability for at least eight and four weeks for et-and me-IPA, respectively. Both IPA derivatives could be suitable for field evaluation of ORV bait uptake in mongooses. Due to the longevity of the marker in mongoose sera, care must be taken to not confound results by using the same IPA derivative during consecutive evaluations.

Oral Rabies Vaccination of Small Indian Mongooses (Urva auropunctata) with ONRAB via Ultralite Baits

“…Additional areas of future research may include immunopathology of the tonsils and oral cavity to evaluate variable vaccine uptake by mongooses in the laboratory [ 16 ] as well as behavioral studies documenting mongoose–bait interaction. Lastly, biomarkers could be used to provide sensitive and quantitative estimates of bait uptake to aid in optimization for this species [ 17 ]. Limited field trials with a placebo ORV bait targeting mongooses have been conducted [ 11 , 18 ], but fewer data are available regarding uptake of ONRAB Ultralite baits by free-ranging mongooses.…”

Comparative Study of Optical Markers to Assess Bait System Efficiency Concerning Vaccine Release in the Oral Cavity of Dogs

“…Upon bait consumption, this marker is taken up by the animal and deposited in bone and teeth, where it can later be detected via fluorescence microscopy [ 14 ]. In addition to tetracycline, other markers have been used to assess bait ingestion, including various types of iophenoxic acids (which can be detected in blood samples), as well as clenbuterol and rhodamine B (which are detectable in both fur and whiskers) [ 15 , 16 , 17 , 18 ]. However, the vaccine bait should not only be highly attractive to the targeted species, but also ensure prompt release of its fluid contents into the oral cavity.…”

Ethyl-Iophenoxic acid as a serum marker for oral baiting of carnivorous marsupials

“…In this study we tested the suitability of Et-IPA as a bait marker in Tasmanian devils, using LC-MS/-MS to directly measure serum Et-IPA. The LC-MS/-MS method described here is similar to recently published methods in (Berentsen et al 2019) and (Berentsen et al 2020).…”