Infectious diseases of livestock are a major threat to global animal health and welfare and their effective control is crucial for agronomic health, for safeguarding and securing national and international food supplies and for alleviating rural poverty in developing countries. Some devastating livestock diseases are endemic in many parts of the world and threats from old and new pathogens continue to emerge, with changes to global climate, agricultural practices and demography presenting conditions that are especially favourable for the spread of arthropod-borne diseases into new geographical areas.
Zoonotic infections that are transmissible either directly or indirectly between animals and humans are on the increase and pose significant additional threats to human health and the current pandemic status of new influenza A H1N1 is a topical example of the challenge presented by zoonotic viruses. In this article, we provide a brief overview of some of the issues relating to infectious diseases of livestock, which will be discussed in more detail in the papers that follow.
At the beginning of the twenty-first century, the world is faced with a changing landscape of infectious diseases that affect man and animals, and that pose significant threats to health and welfare and to the international food security agenda.
Livestock diseases that have devastating outcomes on animal health and that impact on national and international trade remain endemic in many parts of the world. Threats from old and new pathogens continue to emerge, fuelled by changes in the environment climate, hydrology, disruption of ecosystems, etc.
The global human population is expected to increase from approximately 6. Population growth on such a scale poses enormous challenges for food production in general, as an increased demand for 50 per cent more food is expected by , and for livestock in particular, especially in developing countries where material increases in household incomes and accompanying urbanization drives demand for meat and dairy products Delgado et al.
The first year in which more than half the people on Earth approx. Alongside these unprecedented changes in the size and location of human populations and the demands for food, the impacts of environmental change are likely to be detrimental to agricultural production Fresco These factors will therefore drive a requirement for a systematic application of science through the entire food chain in order that all food-producing sectors adapt to changing temperatures, nutrient and water conditions and exposure to harmful pathogens.
The opportunities for scientific innovation are tremendous in number and scope and must be exploited if the world's population is to have enough to eat in the decades ahead.
Control of livestock pathogens will continue to be a highly important component of efficient food production and become associated more overtly with the food security agenda. The world cattle population is estimated currently to be approximately 1.
Estimates of the global number of smaller livestock vary considerably from source to source, but it is generally accepted that there are approximately one billion pigs, approximately two billion small ruminants and more than 50 billion poultry reared annually for food production. Methods of farm production are tremendously varied and bring with them their own particular risks in terms of the introduction and transmission of infectious diseases.
At one extreme is the very low-intensity subsistence livestock farming, particularly of poultry, sheep and goats, that operates in the poorest of the world's rural households and that is critical to sustaining local food supplies, alleviating poverty through income generation and for nutritional status. These animals are often kept under scavenging conditions with little attention to disease control, housing or feed supplementation, suffer a high burden of endemic disease and are likely to be in close contact with other livestock species and humans, and potentially in contact with a variety of non-domestic animals.
At the other end of the farming spectrum are the highly organized and intensive sectors of the poultry industry where the rapid growth rates of birds reared in stocking densities of up to 50 birds in a single shed give the most efficient feed-to-meat conversions of any farm system and provide cheap, high-quality products for the consumer.
This intensity of husbandry can only be done by controlling many infectious diseases that would otherwise inflict severe losses or even prevent intensive poultry production completely, by the administration of vaccines at the start of the rearing period.
For the poultry sector, the emergence of a new pathogen, or a new variant of an old pathogen has the potential to spread rapidly and devastate national flocks, as has happened on several occasions with strains of highly pathogenic avian influenza Alexander , ; Velkers et al. Indeed, some outbreaks of highly pathogenic avian influenza have resulted in the destruction of entire national flocks of poultry and complete restocking has been required from an international breeding company before poultry production could be resumed.
Such vulnerability illustrates the importance of infectious livestock diseases within the context of global food security. Some of the pathogens considered in this series of reviews present an actual or real risk to a serious shortage of food in many parts of the world. Within Europe, the recent incursions of bluetongue virus BTV and subsequent outbreaks of disease have provided a reminder that livestock can quickly become exposed to the ravages of a new disease that takes hold because of changing conditions.
But the CDC is now responding to an outbreak of respiratory disease caused by a novel or new coronavirus that was first detected in Wuhan City, Hubei Province, China.
Bats, civets and pangolins are all commonly sold at live markets in China, she said. Coronaviruses from wildlife are dangerous since they have the potential to mutate, adapt and spill over to new species, including humans. Simmons said that to date, coronaviruses in livestock are not considered reportable diseases because their main effect is as an economic burden to livestock producers. They are known to occur worldwide annually, with some of the most common coronaviruses found in production animals including scours and winter dysentery in beef and dairy cattle, porcine respiratory coronavirus in swine and avian infectious bronchitis in poultry.
The World Health Organization has reported that while another coronavirus, MERS-CoV, is known to be transmitted from dromedary camels to humans, other coronaviruses circulating in domestic animals have not yet infected humans. While coronaviruses have a high morbidity, or rate of illness, in livestock and poultry, they are generally considered to have a low mortality rate, Simmons said. Coronaviruses will affect either the respiratory system or the gastrointestinal system, depending on the species and the age of the animal.
In calves, diarrhea commonly occurs in animals under three weeks of age due to a lack of obtaining antibodies when the calf does not get enough colostrum from the mother to build up immunity. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Tiger shark migrations altered by climate change, new study finds 1 hour ago.
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