Coinfections of African swine fever virus, porcine circovirus 2 and 3, and porcine parvovirus 1 in swine in Nigeria

Farming Practices, Biosecurity Gaps, and Genetic Insights into African Swine Fever Virus in the Iringa and Ruvuma Regions of Tanzania

African Swine Fever Virus (ASFV) genotype II dominates outbreaks in Tanzania's Southern Highlands, continuing to persist as the dominant strain over a decade after its first incursion in 2010. A total of 205 samples from 120 holdings were collected, with 21 confirmed ASFV-positive animals from 14 holdings. Molecular analysis revealed genetic uniformity among isolates, all clustering within ASFV genotype II. Poor biosecurity measures, such as feeding of untreated swill (80% of holdings) and lack of restrictions on visitors (90% of holdings), were identified as risk factors. Additionally, co-infection with porcine circovirus-2 (PCV-2) further complicates disease management. This study underscores the urgent need for enhanced biosecurity and farmer education to mitigate ASFV outbreaks in endemic regions.

Six underreported viral diseases of domesticated and wild swine in Africa: Implications and perspectives

Pig production is increasing annually in Africa as it is recognized as a significant source of income, livelihood and food security, particularly in rural communities. Understanding the circulating swine pathogens is crucial for the success of this emerging industry. Although there is extensive data available on the African swine fever virus due to its devastating impact on pig production, knowledge about the presence of other viral swine pathogens on the continent is still extremely limited. This review discusses what is currently known about six swine pathogens in Africa: classical swine fever virus, porcine reproductive and respiratory syndrome virus, porcine circovirus-2, porcine circovirus-3, porcine parvovirus-1, and pseudorabies virus. Gaps in our knowledge are identified and topics of future focus discussed.

Porcine Circovirus Type 3 (PCV3) in Poland: Prevalence in Wild Boar Population in Connection with African Swine Fever (ASF)

Human health is dependent on food safety and, therefore, on the health of farm animals. One of the most significant threats in regard to swine diseases is African swine fever (ASF). Infections caused by porcine circoviruses (PCVs) represent another important swine disease. Due to the ubiquitous nature of PCV2, it is not surprising that this virus has been detected in ASFV-affected pigs. However, recent data indicate that coinfection of PCV3 and ASFV also occurs. It is still unclear whether PCV infection plays a role in ASFV infection, and that subject requires further analysis. The aim of this study was to assess whether PCV3 and PCV4 are present in the wild boar population in Poland (real-time PCR). The analysis was performed on wild boar samples collected for routine ASF surveillance in Poland, between 2018 and 2021. By extension, the obtained data were compared in regard to ASFV presence in these samples, thus investigating the odds of ASFV infection on the grounds of the PCV carrier state in free-ranging Suidae in Poland. In addition, sequencing of PCV3 and phylogenetic analysis were performed, based on a full genome and a capsid gene. In the current study, we demonstrated the high prevalence of PCV3 in the wild boar population in Poland; meanwhile, PCV4 was not detected. The odds of ASFV infection on the grounds of the PCV3 carrier state in free-ranging Suidae in Poland was more than twice as high. Ten full genome sequences of PCV3 were obtained, all of them belonging to clade 3a. The similarity between them was in the range of 98.78-99.80%.

Molecular Survey on Porcine Parvoviruses (PPV1-7) and Their Association with Major Pathogens in Reproductive Failure Outbreaks in Northern Italy

Successful reproductive performance is key to farm competitiveness in the global marketplace. Porcine parvovirus 1 (PPV1) has been identified as a major cause of reproductive failure, and since 2001 new species of porcine parvoviruses, namely PPV2-7, have been identified, although their role is not yet fully understood yet. The present study aimed to investigate PPVs' presence in reproductive failure outbreaks occurring in 124 farms of northern Italy. Fetuses were collected from 338 sows between 2019 and 2021 and tested for PPVs by real-time PCR-based assays and for other viruses responsible for reproductive disease. At least one PPV species was detected in 59.7% (74/124) of the tested farms. In order, PPV1, PPV5, PPV6, PPV7 and PPV4 were the most frequently detected species, whereas fewer detections were registered for PPV2 and PPV3. Overall, the new PPV2-7 species were detected in 26.6% (90/338) of the cases, both alone or in co-infections: PCV-2 (7.1%, 24/338), PCV-3 (8.2%, 28/338), and PRRSV-1 (6.2%, 21/338) were frequently identified in association with PPVs. Single PPVs detections or co-infections with other agents commonly responsible for reproductive failure should encourage future studies investigating their biological, clinical, and epidemiological role, for a better preparedness for potential emerging challenges in intensive pig production.

High detection frequency and genetic diversity of porcine circovirus 3 (PCV-3) in Namibian backyard farms and warthogs

Since its first identification in 2015, porcine circovirus 3 (PCV-3) has been reported worldwide with a high frequency and in the presence of several clinical conditions, although its impact on pig health and productivity is still debated. Data on the presence of PCV-3 in Africa are, however, limited. A previous study performed on commercial pigs in Namibia failed to identify the pathogen. In the present study, the viral circulation in backyard farms, characterised by lower biosecurity measures and frequent animal exchange between farms, was assessed. The susceptibility of warthogs to PCV-3 infection and their potential epidemiological role were also evaluated. Tonsils from 77 pigs from backyard piggeries and 55 warthogs were collected in different regions of Namibia and tested by PCR. Positive samples were sequenced and compared to PCV-3 strains circulating globally. Forty-two out of 77 pigs (54.54 %) and 12 out of 55 warthogs (21.82 %) tested positive, demonstrating the presence of PCV-3 in the country and suggesting that the high biosecurity measures implemented in the commercial farms that previously tested negative for PCV-3 probably prevented viral introduction. The partial ORF2 gene was successfully sequenced in samples from 27 pigs and 6 warthogs. Genetically, the identified strains were part of 3 distinct groups which included both backyard pigs and warthogs from different regions of Namibia. There is also evidence for the occurrence of multiple introduction events most likely from Asian countries, either directly into Namibia or through other African countries. Considering the strict Namibian regulations on live animal importation, understanding the source of viral introduction is challenging, although semen importation or the habit of feeding backyard pigs with human food waste might have played a role. Pig exchanges between farms for breeding purposes or wildlife movements could also have been involved in PCV-3 dispersal within Namibia. Despite the significant advances in the field, further studies should be undertaken to properly understand PCV-3 epidemiology in Namibia and its impact on pig productivity and wildlife health.

Regional Cross-Sectional Based Study and Associated Risk Factors of Porcine Circovirus 2 in Nigerian Pigs

Porcine circovirus 2 (PCV2) is a swine viral pathogen of substantial economic importance in pig farming globally. However, large-scale surveillance is needed to determine its prevalence and associated risk factors in the Nigerian pigs. We conducted molecular-based surveillance and mapping of PCV2 in southwest Nigeria to assess its prevalence and spatiality. Six hundred forty-eight individual fecal samples were collected from the different age groups of pigs from 67 farms in three southwest states. The polymerase chain reaction technique was used to screen the samples with a specific primer pair. The viral prevalence was determined at individual animal and farm levels. Overall, 145 out of 648 samples (22.4%) and 49/67 farms (73.1%) tested positive for PCV2. The highest prevalence of PCV2 was observed in Oyo State (63/185, 34.1%) and in growers (66/145, 45.5%). Restricting visitors' entrance to the farm was found to be strongly protective for PCV2 (AOR 0.122; p=0.007; 95% CI; 0.027-0.564), while not having a quarantine protocol (AOR 4.445; p=0.041; 95% CI; 1.067-18.5280) and reporting coccidiosis as a common disease encountered (AOR 14.340; p=0.007; 95% CI; 2.094-98.203) on the farm were significant risk factors identified to be associated with the presence of PCV2. This study revealed a higher prevalence of PCV2 in Nigerian swine herds than expected and presented significant spatial clustering of infection in the studied region. It has also highlighted the risk factors driving its spread in the studied area. The research findings underscore the need for a policy decision to promote PCV2 vaccination in the country, which is currently not in place. The availability and use of the PCV2 vaccines, in addition to effective biosecurity measures, will help to mitigate the virus and its associated diseases in the country for sustainable and profitable pig farming, which holds vast potential in solving the problem of hunger and poverty.

Tick-Borne Diseases of Humans and Animals in West Africa

Ticks are a significant group of arthropod vectors that transmit a large variety of pathogens responsible for human and animal diseases worldwide. Ticks are the second biggest transmitters of vector-borne diseases, behind mosquitoes. However, in West Africa, there is often only limited knowledge of tick-borne diseases. With the scarcity of appropriate diagnostic services, the prevalence of tick-borne diseases is generally underestimated in humans. In this review, we provide an update on tick-borne pathogens reported in people, animals and ticks in West Africa by microscopic, immunological and molecular methods. A systematic search was conducted in PubMed and Google Scholar. The selection criteria included all studies conducted in West Africa reporting the presence of Rickettsia, Borrelia, Anaplasma, Ehrlichia, Bartonella, Coxiella burnetii, Theileria, Babesia, Hepatozoon and Crimean-Congo haemorrhagic fever viruses in humans, animals or ticks. Our intention is to raise awareness of tick-borne diseases amongst human and animal health workers in West Africa, and also physicians working with tourists who have travelled to the region.

Porcine Circovirus Type 3: Diagnostics, Genotyping, and Challenges in Vaccine Development

Porcine circovirus (PCV) comprises four distinct species, namely, PCV1-4, with considerable differences between them, resulting in limited crossprotection. PCV2 inflicts substantial economic losses on the swine industry. PCV3 was found to have been circulating before its discovery in 2015. PCV3 is suspected of having a comparable impact to PCV2; however, its characterization studies are still underway. The symptoms of PCV3 infection are similar to those of PCV2 infection. However, PCV2 and PCV3 share a maximum amino acid identity of only 37%, which partially explains the inadequacy of the PCV2 vaccine in protecting against PCV3 infection. Swift measures must be taken to control PCV3, including vaccine development, as it also poses a threat to swine populations. This review synthesizes the recent findings on PCV3 in comparison with PCV2 and highlights the prevailing challenges encountered in vaccine development. Various strategies and innovative approaches to producing PCV3 vaccines, such as using RNA particle technology and baculovirus vectors, are also discussed. Addressing research gaps in diagnostic methods, viral isolation, and vaccine development is crucial to controlling this virus, which poses a threat to swine populations.

A Phylogeographic Analysis of Porcine Parvovirus 1 in Africa

Porcine parvovirus 1 (PPV1) is recognized as a major cause of reproductive failure in pigs, leading to several clinical outcomes globally known as SMEDI. Despite being known since the late 1960s its circulation is still of relevance to swine producers. Additionally, the emergence of variants such as the virulent 27a strain, for which lower protection induced by vaccines has been demonstrated, is of increasing concern. Even though constant monitoring of PPV1 using molecular epidemiological approaches is of pivotal importance, viral sequence data are scarce especially in low-income countries. To fill this gap, a collection of 71 partial VP2 sequences originating from eight African countries (Burkina Faso, Côte d'Ivoire, Kenya, Mozambique, Namibia, Nigeria, Senegal, and Tanzania) during the period 2011-2021 were analyzed within the context of global PPV1 variability. The observed pattern largely reflected what has been observed in high-income regions, i.e., 27a-like strains were more frequently detected than less virulent NADL-8-like strains. A phylogeographic analysis supported this observation, highlighting that the African scenario has been largely shaped by multiple PPV1 importation events from other continents, especially Europe and Asia. The existence of such an international movement coupled with the circulation of potential vaccine-escape variants requires the careful evaluation of the control strategies to prevent new strain introduction and persistence.