Microbiologically the mycoplasmae are gram-negative mollicutes, classified between bacteria and viruses, consisting of cells bound by a plasma membrane and an indiscrete cell wall. These are extracellular pathogens with an affinity for mucous membranes, where they exist as commensals or pathogens. Pathogenic mycoplasmae have a predilection for the respiratory system, urogenital tract, mammary gland and serous membranes. Most of the members of the
C.
mycoplasma mycoides cluster group are the importantpathogens for small ruminants. This group comprises six species and subspecies. In small ruminants, they are known for respiratory disease, kerato-conjunctivitis
(Shaheen, et al., 1997; Shaheen et al., 2000), arthritis, genital disease and mastitis
(Nicholas, 2002). Some of these Mycoplasma species can cause severe and contagious diseases in Goats with significant economic impact
(Cottew et al., 1987). Of the many Mycoplasma diseases,
Contagious Caprine Pleuropneumonia (
CCPP) is a highly fatal disease that occurs in Eastern Europe, the Middle East, Africa and Asia (Table 1)
(Kopcha, 2005).
Contagious Caprine Pleuropneumonia (
CCPP), an OIE List B disease is associated with
Mycoplasma capricolum subspecies
Capri pneumoniae (Radositits et al., 2007).
Contagious Caprine Pleuropneumonia (
CCPP) is a disease affecting Goats and some wild ruminant species. The acute and sub-acute disease is characterised by unilateral sero-fibrinous pleuro pneumonia with severe pleural effusion
(Oie 2014). A variety of mycoplasmae, including
M.
agalactiae,
M.
mycoides,
M.
ovipneumoniae and
M.
Mycoides var.
capri have also been isolated from affected goats culminating into a spectrum of syndromes including fibrinous peritonitis, pneumonia, arthritis, mastitis and abortions
(Radositits et al., 2007). The seroprevalence of the disease in India is recorded to be 33.67 percent
(Ingle et al., 2008). In India, the antibodies against the
Mycoplasma capricolum subspecies
capri pneumoniae have been isolated from Gujarat, Himachal Pradesh, Uttar Pradesh, Maharashtra, Jharkhand and Tripura. Prevalence studies across the enzootic area in Africa and Asia revealed seroprevalence of 14.6% in Ethiopia, whereas in Kenya individual seroprevalence varied from 6 to 90 %. In Mauritius, where
CCPP emerged in 2009, nine of 62 herds tested positive, whereas seroprevalence varied between 2.7% and 44.2% in the other districts investigated in northern Pakistan
(Peyraud et al., 2014). The most favourable epidemiological scenario is the hot humid climate during monsoons in South Asia. Africa and the Middle East have supposed to pose a significant threat to many disease-free areas including Europe. Furthermore, the molecular epidemiology of
CCPP (MLSA) has revealed its identification in Tajikistan and China
(Manso-silvan et al., 2011). It was more likely that the disease might have been endemic to these countries for a long time, as supported by historical clinical descriptions (Fig 1; Table 1).
The molecular epidemiology, cultural characteristics and transmission
CCPP is caused by
Mycoplasma capricolum subsp.
Capri pneumoniae (Mccp). Taxonomically Mccp belongs to the so-called mycoides cluster
(Manso-silvan et al., 2007) and it received its name only recently
(Leach et al., 1993). Its closest relatives are
Mycoplasma capricolum subsp.
capricolum and
Mycoplasma leachii, which may cross-react with Mccp, but the other members of the mycoides cluster, such as
Mycoplasma mycoides subsp.
capri or
Mycoplasma mycoides subsp.
Mycoides and even
M.
ovipneumoniae may also share similarities.
M.
ovipneumoniae is primarily responsible for atypical pneumonia in goats and predispose the animals to other pneumonia-causing bacteria and viruses
(Evermann, 2017). Mccp is highly fastidious and faint turbidity in PPLO liquid medium or colonies on solid PPLO agar medium enriched with horse serum may appear only after 3-15 days
(Shaheen et al., 2001). M.
Mycoides-var-
capri is more often associated with
CCPP in India. Isolation is often unsuccessful and detection may be easier with specific molecular methods such as the PCR
(Woubit et al., 2004; Samiullah, 2013). Mycoplasmas are the smallest free-living fastidious bacteria intermediate. They are about 300 nm in diameter, bound by a triple-layered membrane and unlike conventional bacteria, they don’t have a rigid cell wall of murin
(Robinson, 1997). Their genome size is only one-sixth to one-third of that of
Escherichia coli (Bascunana et al., 1994). Mycoplasmas are phylogenetically related to gram-positive bacteria with low G + C content
(Razin et al., 1983). The Mycoplasma mycoides cluster has two rRNA operons in which intraspecific variations have been demonstrated
(Heldtander et al., 2001).
Mccp was once thought to be a homogenous taxon
(Heldtander et al., 2001; Abu-groun et al., 1994) but the discovery of two molecular markers showed some degree of heterogeneity among strains that opened a further channel for studies on the molecular epidemiology of
CCPP. A typing method with an improved resolution based on Multi-Locus Sequence Analysis (MLSA) developed to trace new epidemics and to elucidate whether the recently identified cases in continental Asia were due to the recent importation of Mccp, proved to be sensitive. The H2 locus, a polymorphic region already in use as a molecular marker for
Mccp evolution, was complemented with seven new loci selected according to the analysis of polymorphisms observed among the genome sequences of three Mccp strains. Asian distinct strains were including the two new strains, were analysed by MLSA resulting in the discrimination of 15 sequence types based on 53 polymorphic positions. Polymorphisms in Mccp strains can be used as epidemiological markers for
CCPP in smaller geographical areas and to study the molecular evolution of this species
(Nicholas, 2002). Eleven polymorphic positions were observed in the sequence of 2400 bp long fragments, obtained from 19 Mccp strains from various geographical locations
(Lorenzon et al., 2002). Similarly, in molecular typing, a good correlation between MLSA (multi locus sequence analysis) groups and the geographic origins of the Mccp strains was observed
(Samiullah, 2013).
CCPP is transmitted directly by an aerogenic route through contaminated droplets of cough and nasal secretions
(Thiaucourt et al., 1996). The outbreak of the disease follows the introduction of an infected animal into a group of susceptible goats
(Oie, 2008). The disease is readily contagious and a short period of contact is enough for successful transmission through coughing
(Thiaucourt and Bolske, 1996; Oie, 2008). No evidence of indirect contact has been shown as the organism is highly fragile in the environment
(Manso-silvan et al., 2007). It is quickly inactivated within 2 min at 60°C but can survive for more than 10 years in frozen infected pleural fluid
(Oie, 2008). Disease outbreak may occur after heavy rain, animal transportation over a long distance
(Oie 2008), poor climatic conditions and primary infections
(Thiaucourt and Bolske, 1996). In most places in the South Asian sub-continent, the disease is usually prevalent during the monsoon season and disappears during the dry hot summer season
(Giadinis et al., 2008). Formaldehyde can inactivate Mccp in 30 sec. at a concentration of 0.05%. A solution of 1.0% phenol can inactivate the organism within 3 min
(Oie, 2008). In primary infected Goats,
CCPP lasts for about two days with high mortality
(Mc martin, et al., 1980) while in other cases it may last for several days
(Oie, 2008). However, in an experimental infection model, Mccp was not isolated from the infected lungs of goats eight-week post-infection due to the development of humoral immunity
(March, 2002).
Clinical manifestations, lesions and diagnosis
The typical clinical signs attributed to
CCPP are hyperpyrexia (41-43°C), high morbidity and mortality rates in susceptible herds irrespective of age and sex. The development of dyspnoea sometimes with grunting and moist rales, continuous nasal discharge that gradually turns seropurulent is specific to this disease besides anorexia and abortion
(Nicholas, 2002; Oie, 2008). In peracute cases, goats may die within one to three days with minimal clinical signs
(Nicholas, 2002). Typical
CCPP lesions occur in the thoracic cavity only
(Mondal et al., 2004) and sometimes affected lungs have abundant pleural exudate and conspicuous pleuritis
(Thiaucourt and Bolske, 1996). The lungs show a peculiar marble shape when examined grossly. Coughing is irregular and nasal discharge is often absent initially
(Oie, 2008). Affected lungs degenerate into a voluminous abscess as a consequence of secondary bacterial infection
(Thiaucourt and Bolske, 1996). Affected lungs become hepatised and take on a port wine colour
(Thiaucourt and Bolske, 1996), with pea-sized yellow nodules surrounded by congestion
(Oie, 2008). The pleural cavity contains an excess of straw-coloured fluid with fibrin flocculations
(Kaliner and MacOwan, 1976; Wesonga, 1993; Oie, 2008; Rurangirwa and McGuire, 2012). Adhesions between the lung and the pleura are very common and often very thick
(MacOwan and Minette, 1977). In sub-acute or chronic cases, the symptoms are very similar to acute cases, but weak
(Thiaucourt and Bolske, 1996).
Confirmatory diagnosis is based on the isolation of Mccp from clinical samples of the lung
(Nicholas and Churchward, 2012). The ideal sample for Mccp isolation is a pleural fluid obtained from a recently slaughtered or live infected goat
(Thiaucourt and Bolske, 1996). Unlike the true
CCPP caused by Mccp, other Mycoplasma infections can spread beyond the thoracic cavity
(Oie, 2008). In the laboratory, the major problem in Mccp isolation is its slow growth and frequent contamination of the culture by other Mycoplasmas
(Thiaucourt and Bolske, 1996; Nicholas and Churchward, 2012). Under an ordinary microscope, the organism has a branching, filamentous morphology in exudates, impression smears or tissue sections, while other Caprine Mycoplasmas usually appear as short filamentous organisms
(Oie, 2008). Mccp and other members of the
Mycoplasma mycoides cluster cross-react in the serological test and share biochemical and genetic similarities, so biochemical and growth inhibition tests are not reliable and specific
(Awan et al., 2009; Oie, 2008). The best and most accurate diagnostic method is the molecular typing of
Mccp (Woubit et al., 2004).
Cultural examination
Several media have been used for the general growth and isolation of Mycoplasmas. Mycoplasma agar and broth media are used for the selective isolation of
Mycoplasma spp. An agar non-selective media under the product code name CC1A (Mycoplasma Experience Ltd. Product), is available that allows the development of Mccp as red colonies over seven days of incubation (MEPG online).
Mccp has been successfully grown and isolated from infected lungs through culturing on Hayflick medium broth (H25P)
(Balikci, et al., 2008; Cetinkaya, et al., 2009; Noah et al., 2011). Similarly modified Hayflicks media have been used for the growth and isolation of Mccp organisms
(Manso-Silvan et al., 2011). Other than Mccp (five to seven days
in-vitro growth), all
Mycoplasma mycoides cluster members grow within 24-48 h
in vitro, producing colonies 1-3 mm in diameter
(Thiaucourt and Bolske, 1996). The
Mycoplasma mycoides var
mycoides (LC) appears as a fried egg or male nipple shaped colonies on Mycoplasma enriched (PPLO agar, marketed by Hi-media) when subsequently stained with Diene’s stain.
Biochemical tests
For preliminary screening, a limited number of biochemical tests are available based on the nutritional capabilities of Mccp or specific enzyme activities
(Noah et al., 2011). Digitonin sensitivity distinguishes Mycoplasmas from acholeplasmas, and serum digestion distinguishes members of the
Mycoplasma mycoides cluster from all other small ruminant Mycoplasmas
(Fao 2012). Phosphatase production separates Mcc from other members of the Mycoides cluster, while metabolic differences (such as maltose positive reaction for Mccp) allow differentiation between Mcc and Mccp
(Barbuddh et al., 2005). The interspeciess variation in some biochemical reactions is often remarkable, rendering their application valueless
(Jones and Wood, 1988). The lack of arginine catabolism in Mccp may help to differentiate it from Mcc
(Noah et al., 2011), but in some strains of Mcc arginine catabolism is reported to be lacking or very difficult to detect
(Jones and Wood, 1988; Rurangirwa and McGuire, 2012a).
Serological tests
Field/farm screening for antibodies to Mccp using a latex agglutination test has been reported
(Rurangirwa, et al., 1987) (Quite a few serological tests are available that are used in the field for the confirmatory diagnosis of
CCPP). Indirect haemagglutination (IHA) and complement fixation tests (CFT) are used to assay the antibody response of goat to Mccp
(Damassa, et al., 1992). The CFT used for the detection of
CCPP is more specific, though less sensitive than the IHA
(Macowan and Minette, 1976; Damassa, et al., 1992). The IHA specificity for the
Mycoplasma mycoides cluster has been evaluated and the results were found to show cross-reactivity between these organisms
(Litamoi et al., 1989; Cho et al., 1976). The latex agglutination test which detects serum antibodies in
CCPP-infected goats is more sensitive than CFT and can be performed under field conditions using whole blood or undiluted serum with a prompt result
(Wamwayi et al., 1989). An indirect enzyme-linked immunosorbent assay (ELISA) has been developed to screen goat serum at a single dilution of antibody to Mccp
(Dighero et al., 1970). The specificity and suitability of ELISA for large scale testing make it an appropriate tool for the epidemiological investigation of
CCPP. Direct antigen detection and blocking ELISA detects antibodies in the serum of naturally or artificially
CCPP-infected goats
(Dighero et al., 1970). Direct and indirect fluorescent antibody tests are the simple, reliable and rapid serological methods applied to clinical samples for the identification of most Mycoplasmas
(Macowan and Minette, 1977). Among many, the indirect fluorescent antibody (IFA) test is the most commonly used and is applied to unfixed Mycoplasma colonies on agar
(Oie 2008). The growth inhibition test (GIT) is the least sensitive and simplest of the tests available for
CCPP diagnosis
(Oie 2008). It depends on the direct inhibition of Mycoplasma growth on solid media by specific hyperimmune serum and detects primary surface antigens
(Rosendal and Black, 1972; Taylor et al., 1997). The GIT is particularly useful in identifying Mccp because they appear to be serologically homogeneous and antiserum to the type strain produces wide inhibition zones
(Oie 2008).
Molecular diagnosis
Until recently, isolation was the only way to confirm the presence of
CCPP. A DNA probe that differentiates Mccp from other members of the
Mycoplasma mycoides cluster was developed
(Bascunana et al., 1994). PCR-based diagnostic systems are used for the rapid detection, identification and differentiation of the
Mycoplasma mycoides cluster members to the serovar and strain level
(Bascunana, et al., 1994). Sequencing of the gene for 16S ribosomal RNA has also been used to develop a PCR-based test where the final identification of Mccp is made depending on the pattern of the products after digestion of the PCR product with the restriction enzyme Pst1 (Type II restriction endonuclease)
(Bolske et al., 1996; Van Belkum et al., 2007). Species identification based on PCR of the 16S rRNA genes and restriction at positions where unique differences occur between the two operons has been demonstrated previously for Mccp
(Van Belkum et al., 2007). An improved resolution method, MLSA (multi-locus sequence analysis) based on the analysis of several genetic markers has also been used for the identification of Mccp
(Manso-silvan et al., 2007). Sequence-based genotyping methods for bacterial typing are technically simple, objective-oriented and portable moreover they allow direct amplification and sequencing of the organism from clinical material
(Manso-silvan et al., 2007).
Chemotherapy and Immunization
The duration of the disease varies according to the environmental circumstances
(Oie, 2008), however, the infected Goat can survive for more than one month or even recover if placed in good rearing conditions coupled with proper treatment
(Samiullah, 2013). A number of anti-mycoplasma antibiotics and vaccines are discussed. Earlier a combination of dihydro-streptomycin sulphate (250 mg/ml) and penicillin G procaine (200,000 IU/mL) was used to treat contagious caprinepleuropneumonia caused by F38 strain of mycoplasma. A single dose of either 20, 30, 40 or 50 mg/kg body weight of the dihydrostreptomycin sulphate led to the recovery of the treated goats. The recovered goats did not transmit
CCPP to susceptible goats housed with them for 2 months. The goats which recovered were found to be solidly immune to an in-contact challenge in which all the control goats died of
CCPP. The treated and recovered goats were found not to be carriers of the organism
(Rurangirwa et al., 1981). However owing to the rapid development of microbial resistance, nowadays it is suggested that macrolides, tetracycline and quinolones are a better choice. In one study Ciprofloxacin, Tiamulin hydrogen fumarate and Oxytetracycline were ascertained to be therapeutically effective in the clinical and bacteriological recovery of
CCPP affected kids in the order of sequence whereas Lincomycin was found to be least effective
(Balikci et al., 2008). However, the use of Tiamulin is restricted as it needs a long withdrawal period in food animals. In another trial study Marbofloxacin at 2 mg/kg B Wt. for three consecutive days was clinically and culturally found to be 100% effective in the treatment of naturally occurring
CCPP in goats
(Giadinis et al., 2008). In one case report, streptomycin-treated goats suffering from natural and experimental
CCPP recovered on the third day of treatment and became completely immune to reinfection with Mccp
(Rurangirwa and McGuire, 2012). The administration of long-acting oxytetracycline prevented morbidity and mortality that controlled further
CCPP spread immediately
(Ozdemir et al., 2005). Danofloxacin was found to be highly effective in the treatment of clinical
CCPP in goats. Commercially available vaccines such as Pulmovac and Capridoll (live) and
CCPPV (killed) vaccines are produced in Turkey and Ethiopia, respectively. Caprivax is an inactivated
CCPP vaccine prepared from a Mccp strain by the Kenya Veterinary Vaccine Production Institute, Nairobi
(Litamoi et al., 1989). The inactivated Mycoplasma strain F38-saponin vaccine in natural
CCPP cases showed 100% protection. In India, the use of attenuated live culture vaccine @ 0.2 ml intradermally at ear tip, is reported to provide immunity for 15 months.
CCPP Vaccine is also prepared at the farm as Longley’s formalized vaccine. Moreover in India IVRI has been preparing
CCPP vaccine since 2000
(Srivastava et al., 2000).
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