Introduction

During the summer months, cattle farms in Spain face a significant increase in the
incidence of diseases transmitted through vectors, especially blood-sucking insects
such as mosquitoes (family Culicidae), midges (Ceratopogonidae), stable flies
(Stomoxys calcitrans), and other diptera.

These vectors act as transmitters of various infectious agents, including viruses,
bacteria, and protozoa, that directly affect animal health, compromise the productivity
of cattle and sheep, and in some cases, affect humans due to the risk of zoonosis.

The following describes the main animal diseases transmitted by vectors in ruminants,
especially cattle, their epidemiology, clinical signs, and incidence in Spain.

It also highlights the essential role that AMBiotec can play in the prevention and control
of these contagious and infectious diseases during the warm months to achieve a
disease-free status.

Bluetongue

Bluetongue is a non-contagious infectious viral disease caused by an Orbivirus of the
Reoviridae family. There are multiple serotypes, and its transmission occurs through
the bite of midges of the genus Culicoides, particularly Culicoides imicola and C.
obsoletus.

Although cattle act as a reservoir, they may exhibit fever, oral erosions, lameness, and
a decrease in milk production. The disease primarily affects sheep, but cattle are also
susceptible to infection.

In the 2024–2025 season, 2,134 outbreaks have been reported in Spain, distributed
among serotypes 1, 3, 4, and 8, significantly exceeding the 1,200 outbreaks of the
previous year. Serotype 1 has predominated in Extremadura, while serotype 8 has
affected Catalonia and the Balearic Islands.

Bluetongue conditions trade restrictions and represents a serious animal health
problem due to its transmission by the bite of mosquitoes of the genus Culicoides.

Epizootic Hemorrhagic Disease (EHD)

Epizootic Hemorrhagic Disease (EHD) is an infectious disease caused by the Epizootic
Hemorrhagic Disease virus (EHDV), also of the Reoviridae family.

SSerotypes 1, 6, and 8 have been identified, with serotype 8 being the most prevalent in
Spain. Like the bluetongue virus, it is transmitted by midges of the genus Culicoides.

Since its emergence in 2022, it has shown rapid expansion through regions such as
Andalusia, Extremadura, Castilla y León, and Cantabria. In 2024, 182 cases of EHD
have been recorded in Spain, a 65% reduction compared to 2023. In Cantabria, cases
decreased from 12,171 in 2023 to 3,164 in 2024, and deaths decreased from 1,907 to
531. In León, more than 400 cattle farms have been affected, with more than 1,100
deaths.

Clinically, it manifests with fever, facial, ocular, and nasal swelling, difficulty breathing,
lameness, and even encephalopathy. It is a reportable disease that affects domestic
ruminants, especially cattle, with serious economic and health consequences.

Malignant Catarrhal Fever (MCF)

MCF is an infectious disease caused by a Gamma-herpesvirus. Although not directly
contagious between cattle, its transmission can be facilitated by blood-sucking insects.

It is common in mixed sheep and cattle farms.

It causes high fever, ocular lesions, erosions in mucous membranes, and neurological
symptoms. Although its incidence is low, it has a high mortality rate. Contact with
infected domestic sheep is the main risk factor.

Bovine Anaplasmosis

Caused by the bacterium Anaplasma marginale, this infectious disease is transmitted
by ticks and biting flies such as Tabanus and Stomoxys calcitrans.

It is common in warm areas of southern and eastern Spain.

It causes anemia, fever, jaundice, and loss of body condition. Seroprevalence in
regions such as Andalusia and Levante reaches between 20 and 40%, reflecting a
notable incidence in cattle. The disease is transmissible by bites and can become
chronic, significantly reducing productivity.

Theileriosis

Theileriosis is a parasitic disease caused by Theileria annulata and T. orientalis,
transmitted by ticks of the genus Hyalomma.
It occurs mainly in extensive farms in southern and eastern Spain.
Clinical signs include fever, lymphadenopathy, anemia, and difficulty breathing. Its
incidence is increasing, favored by climate change and the expansion of vectors. It
affects both cattle and other ruminants, being especially dangerous in calves.

Trypanosomiasis

Trypanosomiasis, caused by Trypanosoma vivax, is also transmitted by biting flies such
as Stomoxys and Tabanus.
Although traditionally considered exotic, cases have been detected in northern Spain
and Portugal in recent years.
Signs of clinical disease include recurrent fever, anemia, infertility, and weight loss.
Although its current incidence is low, it presents a risk of expansion. It is a disease that
affects ruminants and can cause outbreaks if stable vector populations are established.

Schmallenberg Virus

The Schmallenberg virus is an Orthobunyavirus transmitted by mosquitoes of the
genus Culicoides. Although it produces mild signs in adults, its main impact is on
reproduction, causing abortions and congenital malformations such as arthrogryposis
and hydrocephalus.

Outbreaks have been documented in northern and central Spain, with presence in
2018 and 2022. Although its zoonosis has not been confirmed, its impact on animal
health is significant.

Enzootic Bovine Leukosis

Produced by the retrovirus BLV, this infectious disease can be transmitted mechanically
by blood-sucking insects.

Spain is officially free of leukosis, but it remains under eradication and surveillance
programs. Although usually asymptomatic, it can cause lymphosarcomas in a minority
of cases.

Conclusion

Vector-borne diseases affecting cattle in Spain represent a growing challenge,
especially during the summer months.

Pathologies such as bluetongue, epizootic hemorrhagic disease, or anaplasmosis, all
infectious and transmissible by vectors such as mosquitoes and flies, condition animal
health and generate significant economic losses for farmers.

The implementation of preventive strategies that integrate functional nutrition, natural
vector control, and immune reinforcement is essential. In this context, AMBiotec
positions itself as a key ally for farmers and veterinarians, providing effective,
sustainable, and adapted solutions to the Spanish productive environment, actively
contributing to reducing the incidence of contagious diseases in domestic animals and
improving the health of cattle and sheep as a whole.

What are vector-borne diseases and how do they affect ruminants in Spain?

Vector-borne diseases are pathologies that are spread through organisms such as
mosquitoes, which act as vectors. In Spain, these diseases can affect ruminants,
including cattle and sheep, causing significant health problems. These diseases, such
as bluetongue and epizootic hemorrhagic disease, are of particular concern to farmers
and veterinarians because of their ability to cause economic losses and affect animal
health.

What are the main mosquito-borne diseases in Spain?

Among the main vector-borne diseases in Spain, bluetongue and epizootic
hemorrhagic disease stand out. Bluetongue is caused by a virus that is transmitted
through the bite of infected mosquitoes, mainly affecting ruminants. On the other hand,
epizootic hemorrhagic disease, which is also viral, mainly

What role do vectors play in the spread of these diseases?

Vectors feed on the blood of infected animals and then transmit the virus or pathogen
to other healthy animals through their bite. This transmission cycle is critical for the
spread of vector-borne diseases and highlights the importance of prevention and
control measures on farms to protect the health of ruminants.

What impact do these vector-borne diseases have on the health of cattle?

The impact of vector-borne diseases on the health of cattle can be significant. These
diseases can cause serious clinical symptoms, decreased milk and meat production,
as well as increased mortality. In addition, the treatment and prevention of these
diseases can generate high costs for farmers, thus affecting their profitability and
sustainability.

What prevention and control measures can be implemented to protect cattle and
sheep?

To protect cattle and sheep from vector-borne diseases, it is essential to implement a
prevention and control program. This includes the use of vaccines where available, the
elimination of mosquito breeding sites by managing water on farms, and the application
of insecticides. In addition, it is essential to regularly monitor livestock and consult a
veterinarian for virus detection and early detection of any signs of disease.