# Therapeutic applications of IgY in common canine and feline viral diseases

## TL;DR

This review explores the use of IgY immunotherapy in treating viral diseases in dogs and cats, finding it effective in canines but less so in felines.

## Contribution

This is the first scoping review to evaluate IgY immunotherapy for canine and feline viral infections.

## Key findings

- IgY showed faster recovery and improved blood values in canine parvovirus cases.
- Feline studies had limited benefits due to non-specific IgY preparations.
- Most trials were small and non-randomized, indicating a need for more rigorous research.

## Abstract

•This is the first scoping review of IgY immunotherapy in canine and feline viral infections.•Fourteen studies were identified: 10 on CPV-2, 4 on feline viruses (FIV/FeLV/FIP).•Most studies were small, non-randomized clinical trial of moderate evidence level.•Canine studies (CPV-2) consistently reported faster recovery rates and enhanced hematological values, and even prophylaxis.•Feline studies used a non-specific IgY preparation with limited therapeutic benefit.

This is the first scoping review of IgY immunotherapy in canine and feline viral infections.

Fourteen studies were identified: 10 on CPV-2, 4 on feline viruses (FIV/FeLV/FIP).

Most studies were small, non-randomized clinical trial of moderate evidence level.

Canine studies (CPV-2) consistently reported faster recovery rates and enhanced hematological values, and even prophylaxis.

Feline studies used a non-specific IgY preparation with limited therapeutic benefit.

Immunoglobulin yolk (IgY) is the major antibody in birds whose immunotherapeutic potential has been investigated in canine and feline viral diseases. Management currently focuses on supportive care (often insufficient) or prevention using vaccines (slow to develop). IgY is developed against a wide range of antigens, and commercial formulations also exist. Several therapeutic trials and case reports examine IgY as main or adjunctive treatment in feline and canine viral diseases.

To map and summarize the available evidence on IgY-based immunotherapy for viral infections of dogs and cats and assess its reported benefits and shortcomings in a scoping review following the PRISMA-ScR guidelines.

Original English-language studies, focusing on the application of IgY in treating canine and feline viral diseases.

Six databases (Web of Science, Scopus, ScienceDirect, Google Scholar, PubMed, ResearchGate) were searched in October 2024 using combinations of keywords related to IgY, small animals and therapy.

Data on study design, treatment protocol/dosage/outcome and OCEBM level of evidence score were extracted.

In total, 14 studies met inclusion criteria, including 7 clinical trials, 3 case series and 4 case reports; ten investigated CPV-2, while four examined feline viruses (FIV/FeLV/FIP). Most were small non-randomized clinical trials. IgY was administered orally, intravenously, and intranasally. Higher doses generally produced stronger effects. Feline studies used non-specific IgY with limited therapeutical benefit.

IgY-based immunotherapy appeared safe, accelerated recovery and reduced mortality in most studies, but current evidence in feline viral infections is limited and non-specific. Further pathogen-specific trials are required.