Unraveling the Interplay Between Host Genetics, Immunity, and Microbiota in Gastrointestinal Parasite Resistance in Florida Native Sheep

Commodities

• Animals: sheep

Practices

• Animal Production: genetics, parasite control

Improved animal resiliency is
imperative to achieve sustainable productivity and raise healthy
food-producing animals while decreasing reliance on chemical
treatments. Unraveling the role and critical interactions between
genetic features and gastrointestinal microbiome in immune response
development to enhance gastrointestinal nematode resistance in
sheep production has a direct impact on animal welfare, health, and
system profitability. The ability of animals to fight infections is
indicated by the development of immune responses to novel and
recurrent antigens. Immune responses can be broadly classified as
cellular or antibody-mediated immunity. Strong responses of each
type of immunity are associated with improved protection against
infectious diseases and parasites. The strength of immune response
is a heritable trait; therefore, the objective of this project is
to identify the effect of animal genetics and microbiota on the
development of immune responses against gastrointestinal parasites
in sheep. Our hypothesis is that the increased resistance to
gastrointestinal nematodes in the Florida Native sheep breed is due
to enhanced immune responses modulated by genetic factors and rumen
microbiota population. Our objectives are 1)
uncover the contributions of breed and microbiota population to
innate and adaptive immune responses to Haemonchus
contortus infestation, and 2) identify
candidate genes and microorganisms associated with enhanced
immunity and resistance to gastrointestinal parasites. The outcomes
of this research are expected to lead to practical and effective
new solutions that impact animals, farms, consumers, and society as
a whole, promoting more sustainable sheep production practices and
directly benefiting the Southern sheep industry.

In a preliminary study, our group
investigated the effect of breed on antibody-mediated immunity
assessed by immunizing Florida Native and Katahdin lambs with a
foreign antigen, keyhole-limpet hemocyanin (KLH) (Alvarado-Vargas
et al., 2025). Significantly higher anti-KLH IgG concentrations
were observed in Florida Native lambs, suggesting a greater ability
of this breed to mount a humoral immune response. Notably, Florida
Native lambs had lower worm egg counts when raised under the same
conditions as Katahdin lambs, highlighting this breed superior
resistance to gastrointestinal nematodes. Despite numerous studies
on resistance to gastrointestinal nematodes in small ruminants,
there is a critical need to understand the
roles of host genetic factors and microbiome in immunity and their
interplay, and how their relationship modulates host resistance to
parasites. The long-term goal of this
research project is to provide the Florida sheep industry with
novel strategies for improving animal's ability to cope with
gastrointestinal parasites, which have direct impact on economic
viability of sheep operations, animal welfare and health and food
security. The main objective of this
research is to identify genetic features and microorganisms
underlying the variation in immune responses and enhanced
resistance to gastrointestinal parasites in Florida Native sheep.
Specifically, this study is focused on:

Objective 1.
Determine the influence of breed and rumen microbiota population on
the innate and adaptive immune responses to Haemonchus
contortus infestation

1. Generate immune response phenotypes due to Haemonchus
   contortus larvae and adult parasite infestation
2. Determine microbiota composition from rumen fluid samples using
   sequence data
3. Uncover the contributions of breed and microbiota population to
   parasite-specific immune responses

Objective 2.
Compare host genetic features, immune competence and rumen
microbiota composition between parasite-resistant and susceptible
sheep

1. Identify parasite-resistant and susceptible animals using
   weekly worm egg count recorded for 8 weeks after artificial
   infestation
2. Evaluate animals' ability to mount overall humoral and cellular
   immune responses by challenging animals with keyhole-limpet
   hemocyanin (KLH), a foreign antigen
3. Identify candidate genes and microorganisms associated with
   enhanced immunity and resistance to gastrointestinal parasites

The knowledge and tools generated from
this project will have a direct impact on
the profitability and sustainability of sheep operations, reducing
health-related costs, improving animal welfare, and decreasing
reliance on anthelmintics.

The proposed study aligns with the
focus area "Increasing Sustainability of Existing Farming
Practices".