Contagious agalactia of sheep and goats does not occur globally on a predictable pattern and tends to render territories where it breaks out permanently prone to high incidences, regardless of the climatic conditions and the level of economic development of those countries (8). Contagious agalactia of ruminants is an endemic disease and losses in farms are significant. The detrimental consequences of infection are deaths and forced slaughter of sick animals, abortions, birth of sick young animals, reduced milk and wool production, and a high percentage of culled animals during a disease outbreak. The disease is common in developed countries. It is caused by a specific pathogen
Symptomless shedding of mycoplasmas, mainly in milk, may persist for a long time. These insidious infections, associated with carriage in the ears of healthy animals, are difficult to diagnose and control. The main mode of transmission between flocks is related to the sale of carrier animals and contact during transhumance, whereas transmission within a flock occurs through contact, suckling and milking (4).
Although the main aetiological agent of contagious agalactia in sheep and goats is
The spread of this disease is due to several factors, some biotic and some abiotic. Those which are biotic are the nature of the pathogen itself, the area of its circulation in biocenoses, and the route of the pathogen’s entry onto the farm. The influence of husbandry practices subsists in primitive methods of small ruminants breeding, the ineffectiveness of antimicrobial therapy and the lack of appropriate preventive measures (3). Despite the reasonably long-term immunity induced in sick animals, on many resource-poor farms contagious agalactia still breaks out as a stationary process (21). Increasing risk factors for
Clinical signs of agalactia occur during the lambing season, with lactating animals and young animals being more susceptible. It is at this time, if more than 70% of the animal population is affected, that clinical symptoms of agalactia appear (10, 12, 24, 25).
While a moist climate and lower temperatures foster the disease spread, the opposite climatic conditions also have an association with contagious agalactia, specifically the nature of the disease course. According to Stepanenko (36), after 2005 in the southern regions of Eastern Europe and the Mediterranean, long droughts and hot periods were recorded (36). Global warming has a significant impact on climate-dependent sectors of the economy, including agriculture (20, 28). In small ruminant farming in the Odesa region, global warming may manifest in the particular characteristics of contagious agalactia which are observed.
Since the middle of the 1980s in this region, there have been significant deviations of individual weather factors from the average multi-year values. In particular, the frequency of warm winters has increased, the average annual air temperature has risen by 3.5°С and the reserve of productive moisture in the soil has fallen (7). Nine southern districts of the Odesa region have experienced contagious agalactia of sheep and goats since 2003, whereas until 2005 this disease was not registered in the country (expertise No. 511-512 dated October 13, 2005, issued by the Central State Laboratory of Veterinary Medicine of the Ministry of Agrarian Policy of Ukraine). The steppe zone concentrates 915,000 sheep, or 76.4% of their total number in the country. Because of the intensive development of sheep breeding in recent years, the disease may spread to other regions (32, 35). Therefore, defining the spread of contagious agalactia in sheep and goats and the routes of transmission is relevant and necessary.
The purpose of the study was to discover the influence of hydrometeorological conditions on the distribution and disease course of contagious agalactia in sheep in Bessarabia.
The epizootic situation regarding contagious agalactia of sheep was studied during 2011–2021 on sheep farms in the south of the Odesa region (Bessarabia) according to the method of epizootological research of Bakulov
The basis for establishing a definitive diagnosis of contagious agalactia in sheep is the isolation and identification of
The clinical manifestation of contagious agalactia was confirmed by the presence of characteristic signs of the disease (mastitis, lameness and/or keratoconjunctivitis). The mastitic form is most often noted, which is characterised by short-term fever (with a rise in body temperature to 41.5°C) and depression. Then the typical picture of acute fibrinous mastitis is shown, with one or less often two lobes of an udder being affected. Lactation stops. In most cases, atrophy of the affected lobe of the udder is observed in 20–30 days. In 75% of animals, lactation is restored only in the next season. Abortions are not uncommon in pregnant animals infected with mycoplasmas. In severe cases, purulent mastitis is formed, which often ends in a gangrenous process. The articular form is manifested by arthritis. Clinical symptoms include lameness and strenuous gait, joint enlargement, local hyperthermia, and tenderness on palpation. Large joints are affected, most often on one and less often on two limbs. The ocular form is seldom observed, afflicting males and nonlactating queens, and manifested by serous conjunctivitis, accompanied by swelling of the eyelids and mucus. Often the process is complicated by keratitis, which causes pain. If conjunctivitis turns into a purulent form, pain and corneal ulcers are observed, followed by the development of panophthalmitis, which causes blindness.
Data on the amount of precipitation and average air temperature in the studied region were obtained from the Bolgrad meteorological station (Bolgrad, Odesa region). Selyaninov’s hydrothermal coefficient (HTC) was used (34) to assess the moisture conditions of a period with average daily temperatures above 10°C, which is the period of active vegetation. In certain months of the year there are no active air temperatures above 10°C; therefore, the HTC was not calculated for those months. The hydrothermal coefficient was calculated by dividing the amount of precipitation (ΣR) in mm for a period with temperatures above 10°C by the sum of active temperatures (Σt act >10) for the same period, reduced by a factor of 10:
HTC <0.4 was designated very severe drought, HTC from 0.4 to 0.5 was severe drought, HTC from 0.6 to 0.7 average drought, HTC from 0.8 to 0.9 mild drought, HTC from 1.0 to 1.5 sufficiently moist, and HTC > 1.5 meant excessively moist. The obtained data were statistically processed using a Microsoft Excel spreadsheet.
Among the livestock industries in the Odesa region, sheep breeding is not dominant, but is traditionally relevant. The main regions where sheep breeding is developing are the southern districts of the region, collectively Bessarabia. The natural and climatic conditions of Bessarabia largely determine the specifics of sheep breeding. Bessarabia is located in the southwestern part of the steppe agro-climatic zone of Ukraine. Precipitation is one of the most unstable elements of the climate and its amount and seasonal distribution in the south of Ukraine affect the distribution and course of contagious agalactia of sheep and goats.
To assess the humidity of the periods with average daily temperatures above 10°C,
Parameters of the hydrothermal coefficient from 2011 to 2021 in Bessarabia
In 2012, drought prevailed for only three months, and for five months the HTC ratio was in the range of 1.0–1.2, classifying the period as sufficiently moist (Table 1).
Characteristics of hydrometeorological conditions in the south of the Odesa region (Bessarabia) in 2012
Month | Precipitation, mm | Average temperature, °С | Sum of active temperatures (tact > 10), °С | HTC |
---|---|---|---|---|
January | 20.1 | 0.9 | 0.0 | ‒ |
February | 33.0 | 2.4 | 0.0 | ‒ |
March | 39.4 | 11.6 | 360 | 1.1 |
April | 41.5 | 13.5 | 405 | 1.0 |
May | 68.1 | 20.4 | 632 | 1.1 |
June | 46.3 | 22.9 | 687 | 0.7 |
July | 49.9 | 26.7 | 828 | 0.6 |
August | 48.7 | 25.5 | 791 | 0.6 |
September | 52.4 | 21.3 | 639 | 0.8 |
October | 48.8 | 13.6 | 422 | 1.2 |
November | 36.2 | 10.2 | 306 | 1.2 |
December | 53.2 | 2.9 | 0.0 | ‒ |
HTC – Selyaninov’s hydrothermal coefficient
According to the HTC, 2013 was characterised by a mild drought. The most severe drought was registered in 2014, when for six months the HTC ratio was 0.4‒0.5, indicative of severe drought, and for two months it was 0.7‒0.8, a sign of moderate drought (Table 2).
Characteristics of hydrometeorological conditions in the south of the Odesa region (Bessarabia) in 2014
Months | Precipitation, mm | Average temperature, °С | Sum of active temperatures ( tact >10), °С | HTC |
---|---|---|---|---|
January | 30.5 | 1.1 | 0.0 | ‒ |
February | 44.9 | 5.6 | 0.0 | ‒ |
March | 26.4 | 10.9 | 338 | 0.8 |
April | 31.1 | 13.3 | 399 | 0.5 |
May | 28.4 | 18.5 | 574 | 0.5 |
June | 26.1 | 23.1 | 693 | 0.4 |
July | 29.5 | 24.9 | 772 | 0.4 |
August | 27.7 | 25.5 | 791 | 0.4 |
September | 29.1 | 19.7 | 591 | 0.5 |
October | 30.0 | 13.8 | 428 | 0.7 |
November | 42.2 | 9.6 | 0.0 | ‒ |
December | 45.5 | 3.7 | 0.0 | ‒ |
HTC – Selyaninov’s hydrothermal coefficient
In 2015, only two months were sufficiently moist, and during five months drought was the climate condition and an average HTC of 0.8 was found. By contrast, 2016 was quite wet, with an HTC of 1.0. The period from 2017 to 2020 was characterised by moderate and mild drought. In 2021 for five months, the HTC was 1.0–1.2, indicating sufficient moisture, and a mild drought was recorded for three months. The year was quite wet. Thus, interpreting the hydrometeorological conditions, the south of the Odesa region is characterised by severe drought and only once in four to five years is quite wet.
According to our research, the natural and climatic conditions in Bessarabia affect the incidence of contagious agalactia in sheep. Epizootiological monitoring of the incidence of contagious agalactia of sheep from 2011 to 2021 is shown in Fig. 2.
Incidence rates of contagious agalactia in sheep in Bessarabia
The number of studied and diseased animals with contagious agalactia is presented in Table 3.
Dynamics of the incidence of contagious agalactia in sheep in Bessarabia over 11 years
Year | Number of tested animals | Number of seropositive animals | Morbidity, % |
---|---|---|---|
2011 | 210,980 | 20,630 | 9.8 |
2012 | 210,575 | 30,361 | 14.4 |
2013 | 200,415 | 14,112 | 7.0 |
2014 | 198,220 | 12,976 | 6.5 |
2015 | 195,935 | 18,420 | 9.4 |
2016 | 190,800 | 25,010 | 13.1 |
2017 | 179,267 | 19,889 | 11.1 |
2018 | 184,339 | 14,644 | 7.9 |
2019 | 180,972 | 13,412 | 7.4 |
2020 | 168,056 | 15,623 | 9.3 |
2021 | 165,770 | 21,960 | 13.2 |
When the HTC was 1.0 in 2012, 2016 and 2021, these years were characterised as sufficiently moist and in this time the highest incidence rates of contagious agalactia in animals were recorded: 14.4%, 13.1% and 13.2%, respectively. The lowest incidence rates (from 6.5% to 7.4%) were registered in the very dry 2013, 2014 and 2019 with HTC s of 0.5–0.6.
Natural and climatic conditions, namely prolonged drought or sufficient moisture were found to affect the forms of contagious agalactia of sheep and goats. In the sufficiently moist 2012 and 2021, lesions of the udder were most frequently recorded. In 2012, out of 30,361 sick ewes, 21,192 (69.8%) had udder lesions, 1,731 (5.7%) had joint lesions, 2,763 (9.1%) had eye lesions, and 4,675 (15.4%) had mixed lesions (Fig. 3).
Forms of the clinical course of contagious agalactia of sheep and goats in Bessarabia in 2012 (sufficiently moist period)
In 2021, out of 21,960 sick ewes, udder lesions were observed in 15,459 (70.4%), joint lesions in 1,648 (7.5%), eye lesions in 1,141 (5.2%) and a mixed disease course was presented by 3,712 (16.9%) (Fig. 4).
Forms of the clinical course of contagious agalactia of sheep in Bessarabia in 2021 (sufficiently moist period)
In the dry years 2014 and 2019, udder lesions affected only 37.6% and 39% of the animals, while the number of animals with pathologies of the eyes and joints and the mixed form of the disease increased significantly (Figs 5 and 6).
Forms of the clinical course of contagious agalactia of sheep in Bessarabia in 2014 (dry period)
Forms of the clinical course of contagious agalactia of sheep and goats in Bessarabia in 2019 (dry period)
Thus, high rates of sheep and goat morbidity in contagious agalactia in Bessarabia were recorded in fairly humid years, mostly accompanied by udder lesions, and the lowest in very dry years, presenting lesions of the joints and eyes.
According to the World Organisation for Animal Health, contagious agalactia poses a threat to the dairy industry using sheep and goats. The sources of contagious agalactia in sheep and goats are sick animals or mycoplasma carriers, which shed the
Contagious agalactia, occurring on all five continents and often enzootic, is suspected when small ruminants show all or several of the following clinical signs: declining milk production, mastitis, arthritis, keratoconjunctivitis, pneumonia and occasionally abortion. In acute contagious agalactia episodes, these (with the exclusion of abortion) are the most frequently reported clinical signs. Variations occur at the individual and herd level in terms of presence, association and intensity, depending on whether sheep or goats are affected and on herd size, structure, and husbandry practices (5). In large herds, the mastitic form of contagious agalactia is most often registered (14).
Infection is confirmed following mycoplasma isolation or detection. The historical and major cause is
Data indicated the presence of
Most researchers link the seasonality of the disease with the lactation period and explain it by the higher susceptibility of lactating animals and newborns. The disease begins during lambing in the winter and spring and ends after lactation, the summer being when the maximum number of livestock is in lactation (17, 31). Chronic and asymptomatic contagious agalactia of sheep and goats is observed in most cases under favourable environmental conditions – moderately warm and humid summers (38). According to our data, the highest incidence of animals with сontagious agalactia (14.4%) was registered in sufficiently moist years, which is 7.9% higher than in the drier years. This finding concurs with that of other research, in which