PORCINE DISEASES
At present no effective measures for specific prevention and treatment of African swine fever have been developed. The control strategy for the disease is designed for rapid diagnosis of infected animals with subsequent slaughter and decontamination (stamping out). The present review deals with current epidemic situation for African swine fever and examines features of the virus genomics and genetic differentiation of the isolates. The Russian Federation has been ASF-infected since 2007. Since that time the disease has been one of the key problems in pig farming of this country inflicting great economic losses, both directly and indirectly. The disease continues to spread. In January 2014 African swine fever was introduced to Lithuania, then pervaded Poland, Latvia, Estonia, Romania, Belgium and Moldova. Since 2018 the disease outbreaks have been reported in Asia (China, Vietnam, and Mongolia). Specific structure of the virus and long genome, encoding genes with unknown function, and circulation of 24 genotypes and 9 serotypes of the virus hinder the development of ASF vaccine. The article shows that the use of many specific genetic markers during determination of relationship and study of pathways of ASF virus global spread is the most accurate method.
Study results of cellular immunity and cytokine profile of commercial pre-farrow and lactating sows are shown. Before farrow, the animals demonstrated physiological immunodeficiency characterized by relative leukopenia and lymphopenia, decreased T-cell number, higher helper/suppressor ratio providing immunological tolerance in dam/fetus system. Their cytokine profile was specified by relatively deficient interleukin-1β and tumor necrosis factor-α indicative of immune system suppression and high level of γ-interferon involved in parturition and activation of suppressor cells. Post-farrow sows demonstrated higher cellular immunity involving higher levels of leukocytes, lymphocytes and T-cells as well as tendency of T-lymphocyte helper/suppressor ratio reduction being indicative of T-cells’ suppressor activity. The cytokine profile of the sows was specified by the recovered numbers of interleukin-1β, tumor necrosis factor-α and γ-interferon, decreased level of interleukin-2 and interleukin-4 that regulate cellular and humoral immunity, respectively as well as their subsequent increase (in particular, interleukin-2) following animal immunization against parvoviral infection and erysipelas on day 7 post farrowing (Parvoruvax vaccine, Merial, France) and against classical swine fever on day 14 post farrowing (culture dry virus-vaccine LK-VNIVIPFIT). This is due to the formation of the cellular and humoral immunity.
A characteristic feature of African swine fever virus (ASFV) is the ability to escape from host immune response, affecting macrophages and replicating in them. Besides, ASFV - specific antibodies do not completely neutralize the virus. Cytokines are important factors for various viral infection pathologies. The virulence of ASFV isolates may depend on the capacity to regulate cytokine expression by macrophages. Thus, when comparing in vitro and in vivo cytokine production by macrophages, it was established that infection with low virulent virus isolates leads to an immune response with a predominance of cytokines involved in cellular immunity, such as INF-α and IL-12p40, as compared with infection with highly virulent isolates. The aim of this paper was to study the effect of African swine fever virus on the production of IL-10, a pleiotropic cytokine that inhibits synthesis of cytokines and shows a strong antiinflammatory effect. For this, 12 piglets were experimentally infected intramuscularly with a continuous cell culture-adapted ASFV isolate Vero25 at a dose of 10 HAdU per animal followed by control infection of surviving animals with the reference virus isolate Arm 07 at a dose of 1,000 HAdU per animal. Temperature measurements were taken and blood sampling to obtain serum was conducted during the experiment. IL-10 amount in blood sera was determined using Invitrogen test systems (Thermo Fisher, USA). A higher IL-10 level (15.8–173 pg/ml) was observed in blood sera of dead animals infected with a moderately virulent virus, as compared with surviving pigs (4–5 pg/ml). No correlation between the speed of appearance of specific antibodies and IL-10 serum levels has been established. No noticeable effect of the IL-10 serum level prior to infection on the survival rate of animals has been observed. Further studies are needed to establish a causal relationship, including study of the expression of various cytokines during infection with both low- and highly virulent virus isolates.
Diseases associated with porcine circoviruses (mainly with porcine circovirus type 2) have various manifestations, are common in pigs in countries having well-developed pig industry and responsible for significant economic losses. Porcine circovirus type 3 (PCV-3) causing systemic inflammation of unknown etiology in animals was detected the USA in 2015. Later, data on PCV-3 detection in Asia, Europe and South America were published. Analysis of literature data on current epidemic situation on PCV-3 infection in foreign countries as well as the disease clinical manifestations and postmortem lesions are described. Results of molecular and genetic tests of biomaterials collected from pigs in 51 holdings located in 28 regions of the Russian Federation are presented. A total of 280 samples of biological materials of different types (organs, tissues, stillborn piglets) collected from domestic pigs with respiratory, reproductive and neurological disorders, dermatitis and from emaciated pigs were tested and PCV-3 genome was detected in 11 samples from 9 holdings located in 5 regions of the Russian Federation. Porcine circovirus type 3 was detected in lung, bronchial and mediastinal lymph node, spleen tissues from grower and fattening piglets, adult pigs and aborted fetuses. Samples that were positive for PCV-3 DNA when tested with molecular methods (PCR, real-time PCR) were tested for other pathogens. The following pathogens were also detected in 6 out of 11 samples (55%): Actinobacillus pleuropneumoniae, Mycoplasma hyorhinis, Streptococcus suis, Haemophilus parasuis, Mycoplasma hyopneumoniae and Pasteurella multocida. Porcine circovirus type 2 was detected in one sample. Presented test results are indicative of probable combined etiology of respiratory and reproductive disorders in tested pigs that results in various clinical manifestations. Grower and fattening piglets were found to be the most susceptible to PCV-3-associated disease. Further studies are required for identification of actual PCV-3 pathogenicity and its prevalence in the territory of the Russian Federation.
BOVINE DISEASES
The objective of this study was to identify and quantify factors presenting simultaneous moderate or strong influence on gestation length and perinatal mortality (until 4 days postpartum) in Holstein-Frisian dams. The overall gestation length least square mean was 278.2 ± 0.2 days (n = 962). According to the multivariate model (p < 0.001), a shorter gestation length was observed in Holstein-Friesian (–2.0 days) and Red Holstein-Friesian (–3.9 days) breed sires whereas Brown Swiss (2.0 days) and Aberdeen-Angus (2.3 days) breed sires showed a longer gestation length. Primiparous cows and twin pregnancies, as well calving in June and July, shortened gestation length in –1.4, –4.0, –1.9 and –1.8 days, respectively. The perinatal mortality incidence was 7.4% (n = 72) and was more likely to occur in twin pregnancies (p < 0.01) than in pregnancies carrying female (odds ratio = 8.1) or male (odds ratio = 7.9) singletons, as well in primiparous (odds ratio = 2.6) than multiparous dams (p < 0.05). In conclusion, parity and twinning were the major factors which influenced simultaneously gestation length of dams and perinatal mortality incidence. Nevertheless, all studied factors had a significant impact on gestation length and should be considered for reproductive management programs of dairy herds.
EPIZOOTOLOGY
Foot-and-mouth disease is a highly contagious viral disease of cloven-hoofed livestock and wild animals. Europe, North America and Oceania have long been FMD free; at the same time, the virus is widely spread in Asian and African countries. In the period from 2010 to March 2019, FMD was notified to the World Organisation for Animal Health (OIE) by 89 countries of the world. Local FMD outbreaks were also reported in several regions of the Russian Federation throughout this period. The research was aimed at studying some characteristics of the FMD epidemic process in the Russian Federation. The undertaken epidemiological analysis covers the Russian Federation regions where FMD outbreaks were reported between 2010 and March 2019. During the period under consideration, FMD cases were reported in 9 regions of the Russian Federation, mainly in the settlements located in close proximity to the Russia-China and Russia-Mongolia international borders. Most of the outbreaks were caused by serotype O and A FMD viruses. In most cases, FMD was reported in cattle and pigs and, less frequently, in sheep and goats. The analysis of the FMD epidemic situation in the Russian Federation Subjects was performed through epidemic process assessment based on the following estimates: the proportion of infected settlements, epidemic, contagiousness and morbidity rates. The Zabaykalsky and Primorsky Krais have a lead in the number of infected settlements. The highest morbidity rate in pigs was recorded in the Primorsky Krai, in cattle – in the Amur Oblast. The epidemic rate was the highest in the Primorsky and Zabaykalsky Krais. The Primorsky Krai also accounted for the highest contagiousness rates in 2014 and 2019 when FMD occurred on several large pig farms.
The paper presents the results of analysis of epidemic situation on infectious animal diseases subject to compulsory OIE notification: FMD, African swine fever, classical swine fever, lumpy skin disease, sheep and goat pox, and highly pathogenic avian influenza. The paper presents data on the specified diseases situation in the Russian Federation, broken down by Subjects, and also provides a comparative description of the data for 2017 and 2018. Besides, attention is focused on some features of the epidemic process, depending on the season. For a long time the Russian Federation has been infected with several highly dangerous animal diseases, such as African and classical swine fever, FMD, lumpy skin disease, sheep and goat pox, and highly dangerous avian influenza. The specified above infections cause great damage to animal husbandry in the country which has a negative impact on its export potential. Analysis of the ASF epidemic situation demonstrates that the Russian Federation has been permanently infected and there is a trend for the geographic spread of the epidemic. Despite the fact that the number of ASF outbreaks newly detected in 2018 is almost half that of 2017, the situation remains tense. The forecast is still unfavorable. Lumpy skin disease has been reported in the Russian Federation for four years already. Herewith, from year to year the disease has been invading new territories. The HPAI epidemic situation is of great concern as in 2018 82 outbreaks were reported in poultry population which is 2.3 times more than in 2017. Besides, there is a trend for the epidemic extension. Thus, in 2018 avian influenza was reported in previously disease free Subjects of the Russian Federation. In 2018 the Russian Federation remained permanently infected with FMD, sheep and goat pox, and classical swine fever.
The paper demonstrates data on global and national spread of subtype H9 low pathogenic avian influenza in poultry. Due to no need of the mandatory disease notification to the OIE, published data are used for the analysis of the infection spread. Cases of combined low pathogenic avian influenza clinical manifestation in poultry population are described. Challenges of the infection eradication are addressed. Global spread of А/Н9 virus in poultry, its rapid evolution and zoonotic potential require close attention. Since the disease signs and clinical course are similar to the ones of other avian infectious diseases (Newcastle disease, infectious laryngotracheitis, infectious bronchitis, metapneumovirus infection, mycoplasmosis, infectious coryza, etc.), the routine laboratory diagnosis should include tests for low pathogenic avian influenza thus facilitating the rapid response to the threat. Н9 virus circulation is reflected not only in the physical condition of birds and their productivity, but it also affects the live vaccines’ efficacy during scheduled immunizations through the reduction of their protective effect and increase of post-vaccination reactions. In spite of the availability of specific prevention, the opinions of the researchers divided between its opponents and proponents. On the one hand, the vaccination eliminates the economic loses and the virus escape into the environment, but on the other hand, it can aid to “silent” spread of the virus and its established variation that is typical in case of low strength of the poultry population immunity.
VETERINARY MICROBIOLOGY
Staphylococcus aureus is a very dangerous microorganism that causes more than 100 nosological forms of disease in humans and animals, including pneumonia, skin and soft tissue infections, food toxicoinfections, wound abscess, etc. Numerous studies on genotyping Staphylococcus aureus, isolated from humans, food and bovine mastitis have been carried out. The lack of information on the genotyping of these pathogens detected in monkeys living in captivity served as a stimulus to conduct a similar research, since staphylococcal infections in the primates are widespread. The present study is devoted to the study of the polymorphism of a variable region of the coagulase gene and to the typing of Staphylococcus aureus isolates from monkeys of different species kept at Adler monkey farm. 115 Staphylococcus aureus isolates were studied using phenotypic and molecular genetic methods. Genotyping was performed using PCR, real-time PCR and PCR with subsequent restriction fragment length polymorphism analysis (PCR-RFLP). A real-time PCR analysis allowed to classify all Staphylococcus aureus as methicillin-susceptible staphylococci (MSSA). After amplification of a variable region of the coagulase gene, 4 types of amplicons of 600, 700, 800, and 900 bp were generated. This data demonstrates structural differences of this gene in the studied isolates. The coagulase gene of 900 bp prevailed. The use of the Cfo1 endonuclease allowed to identify 23 different restriction profiles of the coa gene, but only three of them predominated. Staphylococcus aureus bacteria with seven types of coagulase gene were found only in the lungs of monkeys that died of pneumonia. The results obtained suggest that these isolates have tropism for lung tissue. Among Staphylococcus aureus isolated from pneumonia cases, isolates with three types of the coa gene prevailed. Staphylococcus aureus of eleven types of coagulase gene can be attributed to the invasive isolates, since they were detected in the tissues of various organs. Staphylococcal infection in monkeys kept at the monkey farm is caused by genotypically heterogeneous population of Staphylococcus aureus.
The paper demonstrates results of testing different modes of Avibacterium paragallinarum inactivation with formaldehyde and thiomersal. The bacterium destruction by 0.20% and 0.10% formaldehyde proceeds at the constant rate thus indicating exponential dependence of the microorganism inactivation processes. This fact allows for calculation of the inactivation rate constant that amounts to 2.94 ± 0.37 h-1 for 0.10% formaldehyde and 5.86 ± 0.72 h-1 for 0.20% formaldehyde. Inactivation using formaldehyde at final concentration of 0.10% at 37 °С and continuous stirring (60 rpm) produces 7.0 dm3 of bacterin at concentration of 9.5 ± 0.2 lg microbial cells (mc)/cm3 in 4.3 ± 0.1 h. Thiomersal demonstrated bactericidal action against Avibacterium paragallinarum at concentration of 0.04% (1:2500) or higher. Herewith, inactivation process is specified by linearity and the inactivation rate constant amounts to 7.92±1.12 h-1. Under thiomersal sublethal concentration of 0.2% (1:5000) the survival curve is of irregular shape. However, the process of the microorganism death is not exponential, and under continuous decrease, the inactivation rate is going to zero thus making impossible the calculation of the inactivation rate constant. Inactivation mode involving use of 0.04% thiomersal at 37 °С allows production of 7.0 dm3 of bacterin at 9.5 ± 0.2 lg mc/cm3 concentration in 5.8 ± 0.1 h. Right after production, the hemagglutination activity of the thiomersal inactivated antigen was higher as compared to formaldehyde inactivated antigen (Р 0.05). The antigen produced using formaldehyde maintains high hemagglutination activity during storage that is critical for high quality vaccine production.
NEWS
FAO press release “FAO director-general graziano da silva hands over helm to qu dongyu with call to improve access to quality food for all”.
ISSN 2658-6959 (Online)