Profesor Dr. Faez Firdaus Jesse Abdullah
Deputy Dean Research and Postgraduate Studies
Faculty of Veterinary Medicine
1) What is Caseous Lymphadenitis?
Caseous lymphadenitis or known as CLA is one of the most significant/ common bacterial diseases among small ruminants (sheep and goat) in Malaysia, and it is caused by Corynebacterium pseudotuberculosis (gram positive bacteria). When a herd of small ruminants is affected by CLA, this disease shows a high morbidity rate despite the low mortality rate.
2) What are the clinical signs of CLA?
CLA causes caseous pus lesions on the external and internal lymph nodes, and it also causes caseous lesion on internal organs in chronic cases. This disease is also known as chronic wasting disease as infected animals will experience chronic weight loss due to the severity of the disease. Based on my knowledge, the lesion observed on the external lymph nodes is not the ultimate or main diagnosis of this disease. Animals that have been infected sub clinically must be screened and separated from the herd. Laboratory tests used to screen this disease must adhere to the manual protocol of the Department Veterinary Services (DVS) Malaysia which is available from the following link. http://www.dvs.gov.my/dvs/resources/auto%20download%20images/560cae1884b1d.pdf.
Based on my own observation and clinical field experience, severe clinical signs of CLA in chronically infected animals include abscesses/lesions on the heart, kidneys, brain as well as the abdominal region. Chronically infected animals will have a low body score (score of 1 to 2 out of 5). From my point of view, this disease will not only affect the productivity of the infected animals, but it will also have a negative impact on the overall production and productivity the farm especially if a large number of animals in the same herd in the farm are affected with CLA.
3) What are the current research on CLA?
In your opinion, what would be the focus of future research on CLA? My research team and I have conducted several experiments on CLA disease. CLA is known to infect small ruminant animals via intradermal route, but our research findings showed that other routes such as subcutaneous, intranasal and oral are also able to cause CLA disease but at a different severity level. We found that the intradermal route causes the most severe infection. The clinical signs and severity of the lesions exhibited by infected animals vary; it depends on whether the disease is acute or chronic. Our findings showed that chronic infection leads to detrimental clinical signs and lesions as observed on animals that were clinically infected with CLA during the chronic period. Recent findings made by our research group showed that CLA infection has a negative effect towards the reproductive physiology of infected animals.
Male infected animals showed a reduction in testosterone hormone concentration which compromised semen quality, whereas non-pregnant female infected animals showed imbalance female hormone production where an increase of progesterone hormone and a decrease of oestrogen hormone were observed. In order to arrive at a conclusion as to whether this disease will cause infertility or compromise the reproductive breeding efficiency of infected animals, further studies need to be conducted. Our research group is in the pipeline to study the breeding efficiency of small ruminant animals infected with CLA, either through experimental infection or natural clinical infection. Also, currently, there is a lack of knowledge and information on the quality of meat of small ruminant animals infected with CLA; thus, our research group is in the process of conducting a study to investigate this matter. We will share our findings next years in the next note series. As for biofilm study involving this causative organism, several experiments have been conducted over the past few years by our UPM and UiTM research teams, and we have obtained interesting results that would help our research group in drafting an effective formula to disrupt the biofilm development of this organism and thus, help us develop an effective disinfectant to ensure farms are free from this causative organism. To have a better therapeutic regime for this disease, new antibiotics need to be developed. Academics and veterinary pharmacologists from FPV, UPM have already started working on this with our research group.
This research focuses on improvising a new formula for CLA antibiotic that is able to penetrate the abscess wall, and the preliminary results of our study have shown promising results. In coming years, our research group hopes to fully develop the new version of the antibiotics so that it can be used in CLA treatment effectively. We will give an update in the next note series. As a preventive measure against CLA, there are several vaccines available from overseas. However, the results obtained by our research group showed that the effectiveness of these vaccines differed in our local setting. Our UPM research group has developed a CLA vaccine (patent has been filed) that will give protection up to 85% to 90%, and this vaccine is based on the local Corynebacterium pseudotubeculosis strain. We are now in our clinical phase and are in the process of increasing the scale of our vaccine production. We will update information on the vaccine once it is ready to enter the market and are available to farmers.
From my professional point of view, future research on this disease should focus on the development of a rapid detection kit that can be used to screen subclinical CLA infected animals, and this is the immediate plan of our research group. Having an easy to use and cheap CLA rapid detection test kit will help farmers to have a better and faster screening, and this will minimise the probability of subclinical CLA in the herds and thus, saves farms from production loss. Another research that needs to be done in future, from my viewpoint is the clinical economic study on the impact of CLA on infected farms. This will provide a detailed analysis, and it allows the development of a projection formula capable of providing an overall and objective picture of economic impact of farms infected with CLA. The formula can be extended to other ruminant diseases as well in the future. I believe the analysis will help farmers (the stakeholders) to have a better picture on the economic impact when a disease infects their farms.
4) How to prevent CLA infection disease from establishing in a small ruminant farm?
Generally, to prevent CLA infection in a small ruminant herd in a farm, the farm must practise and adhere to all biosecurity procedures set out for ruminant farms, test and quarantine new acquired animals before releasing them into the herd and follow all guidelines prepared by the Department of Veterinary Services (DVS) Malaysia.
“Thank you everyone. I hope the information that I have shared helps to refresh and add new knowledge on CLA, and I will share notes on other ruminant diseases in the coming series. Till we meet again in Professor Dr Jesse Note Series, happy reading everyone”.
|Profesor Dr. Faez Firdaus Jesse Abdullah
Deputy Dean Research and Postgraduate Studies
Faculty of Veterinary Medicine
Field of expertise : Ruminant Medicine
 Haemorrhagic Septicaemia (HS) in Buffaloes and cattle
Caseous lymphadenitis (CLA) in small ruminants
 Contagious ecthyma (ORF) in small ruminants
Mastitis in dairy animals
 Acute Phase Protein and Interleukin studies in ruminants
 Diseases in small and large ruminants
 Pneumonia in small ruminant
 Mycoplasma ovis in small ruminant
Date of Input: 06/08/2021 | Updated: 06/08/2021 | mjamil